Spotlight On Young Bird Researchers | Bird Academy • The Cornell Lab

Show Transcript

[Photo: A bird nest with three eggs in it on the ground of a rocky landscape]

[Lisa] Hi everyone, um welcome to the Lab of Ornithology. My name is Lisa Kopp, and I am the visitor experience manager here at the um Lab of Ornithology. And I’m so happy to see you all here this evening, and I want to welcome the live stream audience that is tuning in from all over the world, potentially.

So I want to get through a couple quick announcements before we get started with tonight’s presentation. And the first is to talk about our upcoming Monday night seminar, which is going to be April 25th, right here at the Lab at 7:30 p.m. and um that is going to be featuring author Darryl McGrath who just published a book called Flight Paths: A Field Journey of Hope, Heartbreak, and Miracles with New York’s Bird People.

And she’ll be speaking about the role that women biologists specifically played in saving the peregrine falcon and bald eagle. So that should be a very special presentation, be sure to tune in for that.

But tonight we have something special and unique. You’ll be hearing from three ornithologists relatively new to the field, and some of you know that the Lab has a rich history of working with students at all levels. And we’ve got a really special evening tonight because you’re going to hear from someone in each of those three groups, an undergraduate, a graduate student, and a postdoc.

So our first speaker tonight is Taylor Heaton Crisologo. Taylor is an undergraduate student studying ecology and evolutionary biology. She spent two summers off the coast of Maine working on herring gull nest defense behavior, which you’ll hear about today, and spent last summer in Australia working with superb lyle, lyrebirds in the Blue Mountains.

After earning her undergraduate degree this spring she plans to return to Australia to work as a field tech for a project on red-backed fairy wrens, and while she’s there she plans to visit and um check out Australian graduate schools.

So welcome to Taylor.

[Applause]

[Taylor] Thank you.

[Audio: Herring gull calls]

[Taylor] I’d like to begin my representation with a quote.

[Slide text: “To a hasty visitor, a Herring Gull colony is nothing more than a noisy place…all he remembers afterwards is a chaotic mass of screaming gulls, all flying excitedly round and occasionally swooping down and delivering either a blow or a load of warm, smelly and sticky substance.

To the patient watcher, it is different.” -Niko Tinbergen, Herring Gull’s World]

“To a hasty visitor, a Herring Gull colony is nothing more than a noisy place…all he remembers afterwards is a chaotic mass of screaming gulls, all flying excitedly round and occasionally swooping down and delivering either a blow or a load of warm, smelly and sticky substance.

[Laughter]

To the patient watcher, it is different.” This is from the book Herring Gull’s World written by Niko Tinbergen, the father of modern ethology, or the study of animal behavior.

Good evening.

[Audience cheers and laughs]

[Slide text: Defending the weak: examining temporal patterns of nest defense in the Herring Gull

Taylor Heaton Crisologo, Ecology and Evolutionary Biology ’16

Monday Night Seminar, March 21st, 2016; Photo: Herring gull chick]

My name is Taylor Heaton Crisologo. I’m a senior studying ecology and evolutionary biology, and tonight I’m going to speak to you about the temporal patterns of nest defense in the herring gull.

[Slide text: Parents Invest in Offspring -Parents have a finite amount of energy and resources -Parents compromise their future condition -Offspring benefit; Photos: Bluebird adult at nest box with three nestlings sticking their heads out and begging, and herring gull adult with chicks]

To begin, by show of hands how many of you are parents out there? Parents, all right parents, don’t be shy. Great. So as parents you can probably attest to the fact that across your lifetime you have a finite amount of energy and resources which you can devote to your offspring.

Now with this finite amount of energy and resources in mind, by investing time and energy in your current offspring attempt, you may compromise your future ability to devote those resources to other future reproductive attempts.

The idea being here that if you invest everything in your one current attempt, your prospects for future attempts look pretty bleak.

[Image: Thought bubble coming from photo of a gull, balancing current nest with future nests]

So with this in mind we can consider nest defense as a form of parental investment. So nest defense here demands a balance between two aspects of parental and fitness. Your investment in your current brood, but then also the potential costs for investment to future broods.

So, with this in mind, a selection should favor a balance between your current and your future reproductive attempts. And as it turns out, nest defense behaviors do experience patterns across time.

[Slide text: Offspring Vulnerability Hypothesis -Parents invest in nest defense most when offspring are most vulnerable; Diagram: Adult gull flying with beak open when chick calls for help, and when chick is quiet adult gull does not defend offspring]

So how can we explain how parents may be optimizing investment in their offspring, offspring through changes in nest defense behaviors over time?

One hypothesis, the offspring vulnerability hypothesis, posits that parents will invest most of their nest defense behavior in chicks when they’re most vulnerable. At other times when chicks are less vulnerable, parents won’t invest as much. The chicks are better able to perhaps hide from predators or evade predation by running away, therefore making them less vulnerable, and making the amount of energy that you need to invest as a parent, uh, less.

Therefore we predict under this hypothesis that patterns in avian nest defense would change with the risk of predation that’s posed to your offspring.

[Slide text: Offspring Age Hypothesis -Parents invest more effort in the current reproductive attempt over time -Losses later in the nesting period more costly; Diagram: Adult gull does not defend young chick, but does defend older offspring]

An alternate hypothesis, the offspring age hypothesis, posits that parents will invest more effort in their offspring as the breeding season progresses, and as the offspring age. Here the idea is that as the nest season progresses it becomes harder to re-nest, therefore making your current offspring more valuable to you as time goes on.

Therefore under this hypothesis we would predict that nest defense patterns would increase with the age of the offspring over time.

[Slide text: Why Study Nest Defense? -Studies directly quantifying chick mortality rare -Studies on gulls show varied support; Photo: Taylor wearing a baseball cap and bicycle helmet with a gull standing on her head]

Before I get into my study design, though, I wanted to talk to you a bit about why I think it’s important to study nest defense. Now as you can see here in this photo I’m wearing a helmet. I’m not wearing a helmet because I enjoy long bike rides, romantic bike rides with the gulls in the colony [laughs].

I’m wearing a helmet because as a gull biologist, when you enter the colony you face potential dive-bombs, you face, uh biting, you face, uh, just a lot of pecking [laughs] and pretty intense physical behaviors from these gulls as they’re defending their nests.

Therefore why would we study nest defense, in particular study the nest of a gull? Well, as it turns out studies directly quantifying chick mortality are rare. Other studies have looked at predator density or the conspicuousness of chicks in the nest as proxies of offspring vulnerability.

However, directly quantifying chick mortality could be a great way to test relevant hypotheses in looking at offspring vulnerability. Also studies on larids, or gulls and terns in particular, have showed varied support. This is speculated to be because it’s sometimes hard to tease apart the effects of colony defense versus the defense of individual pairs, thus making it more difficult to assess aggressive behavior.

[Slide text: Study Objectives 1. Quantify offspring vulnerability 2. Quantify changes in parental aggression during the nesting cycle; Photo: Frontal view of gull flying with beak open]

So with that in mind I’ll go over my study objectives. First I wanted to quantify offspring vulnerability, and second I wanted to quantify the changes in parental aggression during the nesting cycle of the herring gulls.

[Slide text: Main(e) Character -Herring Gull (Larus argentatus) -Colony-nesting birds -Chicks are relatively immobile until 7 days of age -Biparental care -Nest defense includes physical contact, intense vocalizations; Photo: Herring gull flying from below]

So I was looking at a population of herring gulls that nest off the coast of Maine and New Hampshire. Gulls are colony nesting birds, and when the chicks hatch out of the egg they’re relatively immobile until they reach about seven days of age. And then they’re able to leave the nest, run around, and also potentially find good hiding places to avoid predation.

Both parents participate in provisioning, brooding, and also nest defense. And for a herring gull nest defense looks like intense physical contact, either by dive bombs which is swooping and aiming for your head, or by bites and pecks, often paired with intense vocalizations.

[Photos: Life cycle of a herring gull from eggs to small chick, larger chick, fledgling gull, and adult gull back to eggs]

So the experience of a gull over its maturation looks a little bit like this. You start with this beautiful egg, which hatches into a fluffy chick that’s relatively immobile until you reach that critical seven-day point. And then your chick begins to look something a little like the chick that you see in the lower right-hand corner.

It looked a little more developed, it’s definitely quicker on its feet, and you start to see the feathers beginning to come in. Now after 45 days the chick looks like it’s about ready to fledge off this island. It’s able to fly away but it carries with it this beautiful mottled plumage of a fledgling bird.

But after three to four years this bird has molted into a breeding plumage adult, completely white. And then it starts the cycle all over again.

[Slide text: Quantifying Vulnerability -Monitored eggs and chicks daily; Photos: Chicks in a nest, and banded adult gull perched on a wooden fence near buildings]

So to address my first objective I quantified vulnerability by entering the colony and monitoring nests every day. When I was monitoring these nests I would mark the number of eggs or chicks present, and that allowed me to get an idea of what the survival probabilities of eggs and chicks look like across the breeding season.

Here you can see a couple of my favorite pictures of gull personalities on the island. On the left hand side we have two adorable chicks, and then on the right hand side we have a gull that was very famous for standing on the porch and begging for food from Shoals Marine Lab students, the island that I worked at. We all lovingly named him Peanut Butter Cookie. And he was really good at stealing food.

[Slide text: Quantifying Nest Defense -Conducted threat simulations at incubation, hatching (day 1), day 9, and day 25 -Captured experiments on video, scored them on scale of 1 – 10 1 No Response → Medium Response → 10 High Response; Photos: Gulls exhibiting no response, medium response (vocalizing), and high response (dive bombing while vocalizing) behaviors]

To address my second objective, quantifying nest defense, I conducted threat simulations across four stages of the breeding cycle. I wanted to look at incubation, the day of hatching, or what we call chick day one, chick day nine of age, and then the age of chick day 25.

To conduct these threats simulations what I would do is I would have a camera set up and then I would walk over to the nest, I would hold the egg or chick present at the nest, depending on the stage of breeding season that the egg or chick was at.

And I would stand present for 60 seconds, and all the while record the response of the parent gulls on camera. Because this was captured on video, I could then return later to these simulation experiments, and score them on a scale of 1 to 10.

So I looked at about 40 nests at the time when I had the most nests present. And I scaled them using this scale here. To explain it a little, a one would look like no response. So this gull is alert, but not necessarily doing much. A medium response would look like some intense vocalizations and frenzied movement, but no physical contact. And a high response would look like a gull with intense vocalizations and a lot of physical contact by dive bombing or biting.

And so here is an example of what a possible very aggressive gull would look like, filmed by GoPro, not by myself. All right, here we go.

[Slide text: Dive Bombing Kelp Gulls – Filmed by Greg Morgan; Video: Kelp gulls vocalizing as they fly in and swoop down, dive bombing the camera, then a dive bomb in slow motion]

Yep, so this gull here is uh, vocalizing and dive bombing the intruder. Oftentimes the gull strikes the target and is able to hit you in the head when it’s dive bombing, hence the helmet. But if you can imagine when you walk into the colony, too. It’s a really kind of crazy place, but crazy fun. And now you have a slow-mo, too.

[Audience exclaims]

[Taylor] [Laughs] Yeah, I’ll let it play one more time, too. Because then you can really get the expression of pure nest defense aggression from this gull coming up on you.

[Audience] Did they hit your helmet?

[Taylor] Yeah, they would hit our helmets, and uh often leave little holes that looked awfully suspiciously like little peck marks [laughs]. There’s an angry call for you.

[Audience question]

[Slide text: Chick mortality is greatest when chicks are young.; Graph: Predicted 5-day survival probability over time (chick day), showing highest survival probability for eggs and older chicks; Photos: Gull eggs and immature gull flying]

[Taylor] [Laughs] We should make a new version called a GullPro that’s covered in poop.

[Laughter]

So what did our results look like? Well first we’re going to look at chick mortality. Well here we’re looking at a graph that shows the predicted five-day survival probability on the vertical axis, and time on the horizontal axis.

First I’d like to direct your attention to the first point, here. That looks like a very high survival probability. This is the survival probability of an egg, and it looks very high because we had relatively low losses at the egg stage for the seasons that we monitored these gulls.

Moving on though, now we’re looking at the time of hatching, and then from here it successively looks at five day intervals. And at the time of hatching the survival probability drops down to about eighty-two percent. So the chances that a chick at this stage of life to survive on to the next interval is eighty-two percent, so four out of five chicks. That’s pretty bleak compared to the rest of this.

Whereas when you’re at day 25, for example, survival probabilities are around ninety-five percent. So things are a lot more optimistic as you age as a chick.

[Slide text: Chick mortality is greatest when chicks are young.; Graph: Predicted 5-day survival probability over time (chick day), with chick days 1-5 and 6-10 highlighted in red; Photos: Gull eggs and immature gull flying]

Therefore we can construct something like danger zone between days 1 and 10 because of the very low survival probabilities. So the take home message here is that for the first 10 days of a herring gull chick’s life, it’s very hard.

Now what did it look like for the parents?

[Slide text: Clutch Stage — Calm; Graph: Proportion of Aggressive Displays by Stage of Nesting Cycle with Clutch Stage almost all medium or low aggression; Photo: Gull eggs in a nest]

Well, I’ll lead you through these results step by step. So here again on the vertical axis, we’re looking at the proportion of high, medium, or low aggressive displays. On the horizontal axis we’re looking at the four stages where I looked at the gull behavior.

Here we’re going to begin with eggs. And so eggs you can notice that there’s a relatively large proportion of low aggressive displays.

Slide text: Hatch Stage — Chaos Ensues; Graph: Proportion of Aggressive Displays by Stage of Nesting Cycle with Clutch Stage almost all medium or low aggression and Day 1 almost half high aggression; Photos: Gull eggs in a nest, and young gull chick]

However, moving on to when chicks first hatch out, you notice that there’s a much larger proportion of high aggressive displays. In other words at this time it’s really difficult to be a gull biologist in the colony

[Laughter]

because all of your birds are really kind of going nuts.

Slide text: Post-hatch — Settle Down; Graph: Proportion of Aggressive Displays by Stage of Nesting Cycle with Clutch Stage almost all medium or low aggression, Day 1 almost half high aggression, Day 9 mostly medium aggression, and Day 25 mostly low and medium aggression; Photos: Gull eggs in a nest, young gull chick, and older gull chick]

Now moving on through time, as you progress to stages day 9 of the chick’s life and day 25 things start to settle down. You start to see an increase in the proportion of low aggressive displays, and again a lot less of the high aggressive displays, so it’s just cruising from there with monitoring these nests.

The take home message here is that parents defend their nest very adamantly right after the chicks hatched out of the egg.

[Slide text: Conclusions -Parents are most aggressive when chicks are most vulnerable right after hatching -Evidence to support offspring vulnerability hypothesis; Photo: Adult gull sitting with young chick on its back]

So what are some of the conclusions that we can make from this? Well, it would appear that parents are most aggressive when their chicks are most vulnerable right after that time of hatching. After about day 7 again the chicks are gaining mobility, perhaps allowing them to better find places to hide or run away from predators. So their vulnerability decreases after that time of being able to move a lot more.

Thus this evidence supports the offspring vulnerability hypothesis, a result which I found really cool. And luckily so did my advisor Dave Bonter, and we now have submit this manuscript and it’s currently in review for publication in a peer-reviewed journal. Woohoo! Cross your fingers.

[Scattered applause and laughter]

[Photos: Taylor holding a blue jay, blue arrows to photos of herring gull chicks (Maine, USA) and superb lyrebird (NSW, Australia), and red arrows to photos of red-backed fairywren (QLD, Australia) and Albert’s lyrebird (QLD, Australia)]

So I’d like to conclude my presentation just with a short note about my experiences at Cornell through the Lab of Ornithology. Over the years at the Lab I have had the chance to really pour my heart into studying biology, and I had the chance to discover that I have a true passion for conducting field research. I’m really crazy about it, just ask anyone [laughs].

So far in my undergrad, I’ve had the chance to study the breeding biology of gulls off the coast of Maine and New Hampshire, I had a chance to go down to Australia to study the awesome vocal mimicry of the superb lyrebird.

And now looking after graduation I’m hopping on a plane to go study uh superb, excuse me red-backed fairywrens at a field side in Brisbane working through the Webster Lab as a field technician and then later a field crew leader. And all the while I’ll be conducting preliminary data and analyses on the Albert’s lyrebird, a bird which I hope to work with for conducting my PhD research.

In short, I could not be excit—more excited about my lifetime spent learning. So with that

[Slide text: Questions?; Photo: Taylor holding a gull chick while crouched on a rocky shore with an adult gull in the background]

do you have any questions?

[Applause]

And also, I can’t forget to put this slide up. I’d really like to thank my advisor, Dr. Dave Bonter. He’s brought me through every stage of every process in research. When he first met me I was a freshman who had no idea what I was doing.

[Slide text: Acknowledgements Dr. David Bonter The Cornell Lab of Ornithology Biology Research Fellowship Shoals Marine Lab The Bonter Lab Group 2014 Colleagues: Collin Hertz, Sara Gonzalez, and Lindsay Moulton 2013 Colleagues: Michelle Moglia, Shailee Shah, and Sarah MacLean]

So, thank you, Dave. And everyone else [laughs].

Okay, so I’ll take any questions if you have any.

Sahas?

[Sahas] Are the individuals marked? Are males more aggressive than females or are females more aggressive than males?

[Taylor] Yeah, so to repeat the question we were asking if males are more aggressive than females, and whether the birds were marked.

So we did have individuals banded with field readable bands. So for those birds if we were able to take blood samples back to the lab to sex them we knew the sex of the bird.

However, that was very few of the birds that were being monitored. And unfortunately since it’s very hard to discern the sex of a herring gull we were not able to conduct those analyses.

However, if I could do it all again I’d have all of those birds banded, and know every single thing about the individuals and then look at nest events from there. But great question, thank you.

Anyone else? Yes?

[Audience] Along those same lines, did you know anything about the relative age of the breeding birds, and was there a difference between first year breeder aggression versus older, more experienced birds? Were they more aggressive or less aggressive?

[Taylor] Yeah, great question, thank you. So the question was whether there was a difference between aggressive behavior of younger birds versus older birds. So luckily we can tell the younger birds because, it’s, although it’s not too, too reliable I don’t think. Often younger birds that come to nest will have residual spots in their breeding plumage, like on their tail feathers, or on their wing feathers.

We didn’t really look for differences in aggression between young and older birds. Um, however something that has been looked at is the differences in the nest survival probabilities of younger versus older birds. That’s something that I think would be more interesting to look at cuz sometimes it seems like the younger birds have less luck. But no, that’s not something we addressed. Thanks.

Any other questions? Yes?

[Audience] Does being aggressive work in terms of keeping your chicks alive?

[Taylor] Okay, so…

[Audience] So are the most aggressive ones doing best at keeping their chicks alive during those stages?

[Taylor] Yeah, and so that’s something that I wanted to look at. Um, so the question was whether more aggressive birds were more likely to have chick that were um fledging, or like more successful nests.

That was something that I don’t think we could look at because of lower uh… sorry, we didn’t have enough nests to really look at, and compare those data. But that’s a question that I really wondered about. Something else I wanted to know also is if more aggressive birds are more likely to be in the vicinity of other aggressive birds, or if wimpy birds are more likely to crowd around the very aggressive birds to kind of mooch off of those aggressive benefits. But no, unfortunately that was a question that I could not answer.

Hopefully another future gull biologist will look. Any other questions? Yes?

[Audience] Um, were the, uh. I forget my question. Never mind. I’ll let somebody else go.

[Taylor] Oh, it’s okay. Come, we’ll talk later. Yes?

[Audience] Was mortality only related to predation or were there other reasons for mortality?

[Taylor] I’m so glad you picked up on that. That’s a great question. So the question was whether mortality was mostly due to predation, or to other sources. Well on the island we were considering two main factors of predation being, or excuse me, of mortality being predation or starvation of the birds, or weather effects. We didn’t see much if any at all starving of the birds on the three years that I was monitoring.

There we’d be looking for a decrease in the weight of the chick over time, and then the chick being dead.

Although we couldn’t quantify it because we didn’t know what was happening in the colony when I was not there monitoring, there were often times when I’d go into the colony and I’d see a great black-backed gull, the larger heterospecific that nests on the island, with the legs of my chicks sticking out of its mouth [laughs].

So there was a lot of predation on the island from the great black-backed gulls, and that’s what we think is accounting for most of the chick losses. Thanks. Yes?

Oh you remembered your question?

[Audience] I did remember it.

[Taylor] Okay.

[Audience] And that partly answers my question about whether there was, uh, the herring gulls were predating on their own nests, um obviously the greater black-backed was doing some of that, were there other birds that were doing the predation as well?

[Taylor] No, so we’d be looking mostly at great black-backed gulls. And herring gulls who, from my experience won’t actively go of, go after the chicks of other birds in the nearby nests. However, the exception is when there was a territory dispute, and the chicks of one nest would wander over to the chick, to the territory of another nest. Then the gull parents would actively defend that nest site, and if the chick didn’t get out of there quick enough, it would be killed by the other parents. Great question, thank you.

Yes?

[Audience] I have a two parter. Um, could you describe the most intense number ten you experienced?

[Taylor] [Laughs]

[Audience] And also how would you rate the intensity of popcorn and french fry hunting compared to

[Taylor] [Laughs]

[Audience] They don’t seem to be quite as aggressive when they’re looking for food.

[Taylor] Okay, yeah so two questions. The first one, I’ll address. So it was what would be an account of the most aggressive bird? Okay, so there was 14H210, there was this nest, we monitor them by these nesting codes. I remember that, it’s ingrained in my head because this bird lived in this crevice [makes a v shape with her two hands]. So its nest was down in here [uses one hand to point to the bottom of the v], and so every day when I’d go to monitor that chick or egg that was at the nest, or chicks or eggs, I would have to climb down to really peek in and make sure that I was seeing who was there.

But the gull parents were really smart, and they figured out that I’d have to go down there, so they’d meet me halfway, and all the while be pecking at me, and squawking at me, and the other one would take turns dive bombing my head while the other was in the crevice harassing me [laughs] but they were great parents.

And the second question was why does… um? Or why don’t gulls seem like they’re as aggressive when they’re foraging?

[Audience] Yes.

[Taylor] Like for french fries and popcorn. My best guess would be that maybe you’re seeing gulls outside of the breeding season. And so my impression is that a gull, or any bird, during the breeding season versus the off-breeding season are two very different characters.

So gulls during the breeding season have a lot invested in those chicks and eggs, and so they will fight to the death for them. That said, you know I, they might also fight to the death for french fries sometimes [laughs].

[Laughter]

[Taylor] Uh, I don’t know. I haven’t observed many french fry things, although once a gull did regurgitate a hot dog, like a full hot dog, on my friend’s shoulder [laughs].

[Laughter]

[Taylor] And it actually bounced off, it was funny [laughs].

[Laughter]

[Taylor] Are there any other questions?

Okay, I think that’s…

[Applause]

[Slide text: Please stand by: The Cornell Lab of Ornithology Monday Night Seminar will continue in a moment; Photo: Cornell Lab of Ornithology building from the outside with the pond in the foreground]

[Lisa] Thank you, Taylor. That was great. Um so next up we have Sahas Barve, who um is a PhD candidate, also in the Ecology and Evolutionary Biology Department. He is an avid birder from India, and has been doing field work in the Himalayas for the past four years.

Um Sahas is interested in bird conservation on mountains around the world, and according to him, he’s interested in science communication and making natural history cool again.

[Laughter]

So welcome Sahas.

[Applause]

[Sahas] Cool, okay um so I’m going to talk to you, transport you guys, to the Himalayas in India where I’ve been studying physiology in, in birds.

[Slide text: Hypoxia and Himalayan birds: Lowlanders at the base and summit.

Sahas Barve, Dhondt Lab www.sahasbarve.com Cornell Lab of Ornithology, Cornell University, Wildlife Institute of India; Photo: View of the Himalayas with the foreground in shadow]

I’m Sahas Barve, I’m in the Andre Dhondt lab and I’m a graduate student here at the Lab of Ornithology, and in the department of ecology and evolutionary biology.

[Photo: Street in Bombay crowded with people and vehicles]

So I grew up in a really tiny, quaint town called Bombay,

[Laughter]

which is inhabited by about, it’s about 200 hundred thousand people, um and obviously being a birder I needed to find a better place to bird in.

So um

[Photo: Sahas in a forest looking up through binoculars]

for the last few years I’ve been

[Photo: The Himalayas, with snowy peaks in the distance and a snow-covered slope in the foreground]

going back to a really tiny village in the Himalayas with a permanent population of about nine people, and significantly better birding.

But I chose this place because it’s a Himalayan state and India has about 1,300 species of birds, and this state alone, which probably takes up less than 2% of the country’s total area, has about

[Slide text: 691 species; Photo: The Himalayas, with snowy peaks in the distance and a snow-covered slope in the foreground]

691 species.

So it has more than half of all the birds found in India, which is, which is crazy right, so it’s the right place to be for a birder. But the question is why are there so many birds in this state? One of the main reasons is that it’s a mountainous state.

[Slide text: Mountains around the world; Image: Simple line drawing of a mountain with different colored bird silhouettes at various heights up the mountain with lines separating them, representing different species at different elevations]

And on mountains around the world you get this sort of pack, stacking up of species as you go up the elevation. So you have bird species that are found at different elevations um, and they get stacked up. And each species thus has an upper limit and a lower limit of distribution, right.

[Slide text: Adirondacks National Park; Image: Simple line drawing of a mountain with drawings of a black-capped chickadee lower on the mountain and boreal chickadee higher up]

So you have, but I mean, as I said that happens in in mountains around the world, so if you go to the Adirondacks here, you have boreal chickadees at the, in the high elevations, and black-capped chickadees in the lower elevations.

[Slide text: Western Himalayas; Image: Simple line drawing of a mountain with drawings of six different sunbird species at various elevations]

If you go to the Western Himalayas where I work you have uh how many is that? Six species of sunbirds uh going all the way from purple sunbirds in the low elevations to fire-tailed sunbirds in the high elevations. Uh, and looks like from at least this figure the length of the tail also goes on increasing with elevation, but I don’t want to talk about that.

But the thing to remember is that

[Image: Simple line drawing of a mountain with different colored bird silhouettes at various heights up the mountain with lines separating them, with the line below the red bird labeled “Lower Limit” and the line above it labeled “Upper Limit”]

each bird has a distinct upper limit and a lower limit of distribution. Um and one of the most interesting questions in ecology has been why is that? Why are birds limited to certain elevations?

[Slide text: What determines the distribution of birds on mountains?; Photo: Mountain with yellow flowers in the foreground]

So can someone tell me what, what might change across, across the elevational gradient? What might change with elevation?

[Audience responds]

[Sahas] Temperature, vegetation…

[Audience] Oxygen.

[Sahas] Oxygen, great, thank you [laughs].

[Audience laughter]

[Audience] Insects.

[Sahas] Insects, yeah so a bunch of different things change. And so the easy answer to this question is just a bunch of different,

[Slide text: What determines the distribution of birds on mountains? A mix of ecological and environmental factors; Photo: Mountain with yellow flowers in the foreground]

a mix of ecological and environmental variables change with uh, with elevation. So… uh…

[Slide text: What environmental factors change with elevation?]

I study

[Slide text: Hypoxia Physiology; Images: Drawings of various songbird species; Photos: Sahas sitting near a tree with his equipment, and a machine that measures oxygen levels]

hypoxia physiology uh, or the reduction in oxygen due to part—reduction in partial pressure of oxygen. So it’s technically not the amount of oxygen, it’s the number of molecules in the air of oxygen. Um and I study how birds cope with what is called hypoxia.

Okay,

[Slide text: Hypobaric Hypoxia -Constant feature around the world -Is not affected by latitude or temperature; Photo: Mountain climbers near the top of a snowy mountain]

so there are some things really cool about hypoxia, and that’s, it’s that it’s a constant feature around the world. So if you go at, go to 3000 meters anywhere in the world the partial pressure of oxygen will be very, very, very similar to any other place in the world that is at 3000 meters, right.

So that makes it sort of a uniform constraint for anything that lives up there at those elevations. The second thing is that it’s not affected by any other environmental trait, like temperature, right. So even if the air temperature is potentially 30 degrees Celsius or minus 30 degrees Celsius the amount of hypoxia will be the same.

[Slide text: Hypoxia- Tibetan plateau, Ethiopia, Andes; Photos: One to two people wearing traditional clothing from each location]

Hypoxia has been studied in a number of human populations because uh evolutionarily speaking we have these, this natural experiment with three different populations of human beings Ethiopians, Andeans, and Tibetans have sort of independently colonized high elevation areas around the world, and they have sort of adapted to those areas.

The only sort of caveat in that is that the amount of time each population has spent at high elevations is different. So Andean populations have probably lived in uh, in the high elevations only a little more than a thousand years, while Tibetan populations have been around for about three thousand years. Uh and that actually has brought about a bunch of differences in, in the way they cope with hypoxia.

So Andeans show what is called a very lowland response to to hypoxia. So what happens in our bodies when we go to a high elevation is that um, to increase the transport of oxygen from the air to the blood uh, our bodies make more RBCs, right, they make more red blood cells, which is called the hematocrit of blood.

So you increase hemoglobin concentration of the blood by increasing the hematocrit of blood. The problem with that is that the more RBCs you pack into blood, the more viscous the blood gets, right. So after a point of time it stops being blood, it starts being more like tomato ketchup. And uh pumping tomato ketchup is much, much more difficult for your heart than pumping blood.

So high viscosity is actually maladaptive after a certain range, right? So Andeans showed this sort of a maladaptive trait where they have extremely high levels of hematocrit throughout their lives. And Andean populations actually have one of the highest rates of miscarriages um in the world because pregnant women form clots very easily.

As opposed to Tibetan populations, who have been around for a long time uh, show, show sea level levels of hemoglobin concentrations. So their hemoglobin concentration is the same as a person at sea level, and that’s because they have other ways to get around hypoxia. What they do is uh Tibetans have bigger lungs, so they have bigger lung capacity.

But they also have nitrous oxide, which is laughing gas, in their, in their arteries. And what nitrous oxide does is it’s a vasodilator. So it keeps uh the, it keeps the blood vessel dilated, and hence allows a lot of blood to pass through. So circulation is better, and their lungs are better. So they can transport oxygen much more efficiently.

[Slide text: Hypoxia; Photos: Llama walking, two bar-headed geese in flight, chicken viewed from the front, goat kid jumping, and a wild yak charging]

Hypoxia has also been studied in a number of domestic and wild animals. So one of the champions of hypoxia, sort of um champion of hypoxia are bar-headed geese, which are up there. Let me see if I can, yeah. So these are bar-headed geese. They are known to fly over the, over the Himalayas, um and, but then there are some terrestrial animals like wild yaks that have been studied, and in the Andes llamas.

Uh and chickens have been studied a lot because chickens fail to lay eggs above 2,000 meters I think, and people have been trying to make chickens to lay eggs because highlanders like eggs.

Um the reason birds are really, really cool

[Slide text: Birds and hypoxia -Cold + Hypoxia -Flight; Images: Drawings of black-throated tit and Himalayan bluetail]

to look at sort of from a, from a physiology, hypoxia point of view is two reasons. So first is that the, birds have only shivering thermogenesis. So a lot of mammals have what is called brown fat um, which is really, really efficient at heat production. But birds uh, don’t have brown fat and have shivering thermogenesis. So they have to shiver to produce heat in their body, right.

So shivering is a muscular, is muscular exercise, and muscles need oxygen, right. So if you are in a cold and hypoxic place, and you can only shiver to keep warm you’re in big trouble, right.

The other thing is trying to fly in really hypoxic conditions. So flight uh requires about, so birds amp up their metabolic rates 10 to 12 times when they’re flying. And so being able to fly in hypoxic conditions is really difficult.

To give you a small example of how, how tolerant birds are, a chickadee here, consider chickadee here in in the dead of winter, it’s it, it’s often minus 40 degrees Celsius, the air temperature is. And a chickadee’s core temperature is 40 degrees Celsius. So there’s an 80 degree Celsius gradient in probably a two-centimeter difference from the air to the core of its heart.

So birds have to really, really fire their furnace to keep warm.

Okay so let’s take a segue and go to

[Photo: Mount Everest]

the highest point on earth.

So this is the, this is Mount Everest. And um at the top of Mount Everest

[Slide text: 32% O2 with arrow pointing to the top of the mountain; Photo: Mount Everest]

the partial pressure of oxygen is only thirty-two percent. So it’s about one-third uh that at sea level. And a piece of trivia is that Mount Everest

[Slide text: George; Photo: George Everest]

is named after George Everest [pronounced eve rest], so we’ve been pronouncing Everest wrong all the time.

[Laughter]

And old George never saw Mount Everest himself. He, but he was a surveyor general of the Indian uh, so surv—he was the surveyor general of Survey of India, which made, basically made the first map of India.

[Slide text: Sir Edmund Hillary, Tenzing Norgay; Photo: Hillary and Norgay wearing mountaineering gear]

Mount Everest was summited by two people Sir Edmund Hillary and Tenzing Norgay, who was not a Sir for some reason. Um, but their life histories are actually really cool, and I’ll, and you’ll soon know why.

So Edmund Hillary,

[Slide text: Lowlander Hillary, NZ, Aukland; Images: Hillary and Aukland, and a map of New Zealand]

let’s call him Lowlander Hillary because he was born in New Zealand and he was born in Aukland. Uh Edmund Hillary was a beekeeper and then joined the Royal Air Force in World War II, and he was a mountaineer. So he went from sea level to the top of Mount Everest.

[Slide text: Nepal, Highlander Tenzing; Images: Photos of Norgay and a village in Nepal, and a map of Nepal]

On the other hand Tenzing Norgay was a, was a highlander. So sherpa villages are on the border of China and, and Tibet, so Nepal and Tibet. And so Tenzing Norgay was born in a really, really high elevation place.

[Slide text: Difference in elevational movement; Image: Simple line drawing of a mountain with a drawing of a bird near the bottom of the mountain labeled “Hillary Robin”]

Like Hillary and uh Tenzing Norgay

[Laughter]

we have, we have birds. So every year millions of birds of hundreds of species around the world travel from the low elevations

[Animation: “Hillary Robin” bird drawing moves to the top of the mountain]

in the winter to high elevations where they breed, right. So let’s call all of these birds Hillary robins, okay.

[Laughter]

On the other hand,

[Slide text: Difference in elevational movement; Image: Simple line drawing of a mountain with a drawing of a bird near the top of the mountain labeled “Hillary Robin” and a drawing of a different bird midway up the mountain labeled “Tenzing bushtit”]

there are these birds uh that are uh that live at the same elevation all year round, right.

[Animation: “Tenzing bushtit” bird drawing moves around midway up the mountain]

So they face the same amount of hypoxia all year round, as opposed to Hillary robins that live in oxygen-rich environments for about seven to eight months of the year, and oxygen-poor environment for four, four months of the year.

So then the question is do these two different kinds of birds,

[Slide text: How do they respond to hypoxia?; Images: Drawing of bird labeled “Hillary Robin” and drawing of a bird labeled “Tenzing bushtit”]

do Hillary robins and Tenzing bushtits uh respond to hypoxia differently, right? So what we can predict

[Slide text: Two ways of combating hypoxia 1. Lowlander response (maladaptive)- Increase hemoglobin by increasing hematocrit (volume of RBCs in blood); Image: Drawing of bird labeled “Hillary Robin”]

is that because most of their time is spent in oxygen-rich environments, Hilary robins will show a lowlander response where they increase the oxygen transport by increasing the hemoglobin concentration by increasing hematocrit, right.

So they will have high hemoglobin concentration and high hematocrit, which means that they have a lot of RBCs in their blood.

[Audience] Ketchup.

[Sahas] Ketchup, yep. On the other hand

[Slide text: Two ways of combating hypoxia 2. Highlander response (adaptive)- Physical and biochemical changes in addition to increasing hemoglobin, without high hematocrit; Image: Drawing of bird labeled “Tenzing Bushtit”]

we can predict that Tenzing bushtits that live at high elevations all year round will have some other biochemical ways to, in addition to increasing the hemoglobin concentration, to transport oxygen effectively from the air to get to their bodies. Okay, um, so my

[Slide text: Kedarnath Wildlife Sanctuary; Photo: Kedarnath Wildlife Sanctuary with large rhododendrons in bloom on the mountainsides]

research was done uh in a beautiful place called Kedarnath Wildlife Sanctuary. So these are, so this is, this is the photo taken at about 3,000 meters or 10,000 feet. There are these giant rhododendron trees so all of oops, sorry.

[Slide text: Kedarnath Wildlife Sanctuary 1000m – 4000m 244 bird species 1000 m- 3500m Winter & Summer hemoglobin, hematocrit; Image: Map of India with blue star marking location of Kedarnath Wildlife Sanctuary in the northwest]

[Slide text: Kedarnath Wildlife Sanctuary; Photo: Kedarnath Wildlife Sanctuary with large rhododendrons in bloom on the mountainsides]

Uh all of these are rhododendron trees that are in in bloom, um, and it’s it’s absolutely stunning place.

It’s in the northwest corner of India where that star is, um and we just, we actually sampled a really, really small part of the sanctuary. And we still saw, we documented more than two hundred forty-four species.

It’s an incredibly, incredibly diverse place. Um… okay

[Slide text: Bird diversity Dixit, Joshi, Barve accepted; Graph: Species richness in winter and summer at Siroli (1500m), Ansuya (2100m), Kanchula (2600m), and Chopta (3000m) showing decreased species richness with increased elevation in winter, and smaller decreases in species richness with increased elevation in summer]

but that diversity of 244 is not, is not distributed uniformly. Um you have species that live uh at low elevation, species that live at high elevations. In the winter there are a lot of species, about 140 species at low elevations, but only about 30 species that live at high elevations.

Uh in the summer though you have about 100 species that live at high elevations, and how does that happen? That happens because

[Slide text: Bird diversity Dixit, Joshi, Barve accepted; Graph: Species turnover in winter and summer at Siroli (1500m), Ansuya (2100m), Kanchula (2600m), and Chopta (2800m) showing lower species turnover with increased elevation in winter, and the highest species turnover at the highest elevation in summer]

there are a lot of Hillary robins that migrate from southern India in the foothills to breed at these high elevations. So both these high elevation places uh get about 70, 60 to 70 species that come to breed only there, all right. So… um

[Slide text: 1000 m-3500m Winter & Summer hemoglobin, hematocrit; Images: Drawings of various bird species, and photo of mountain landscape]

this is what um I did. I basically sampled birds between 1,000 meters and 3,500 meters in winter and summer. Uh and I collected data on hemoglobin concentration and hematocrit.

[Photo: Himalayan mountain scene with buildings in the foreground, sun illuminating the tops of the mountains, and blue sky with some clouds]

So I liv—so as, as you can, if you’ve been in the mountains you can well understand seasons can, like the temperatures and uh weather conditions can change very quickly. So this is the same spot at 7 a.m. and

[Photo: Himalayan mountain scene with buildings in the foreground, snow covering the ground and tops of the buildings, and mountain peaks no longer visible because of clouds]

at I think 9:30 a.m. or something.

[Audience exclaims]

And to prepare for that we uh have to do a lot of really,

[Photo: Three people doing yoga outside near small trees and other vegetation]

really hard training. Um

[Video: From previous photo, three people exercising outside near small trees and other vegetation; Audio: Inspirational music plays]

we are constantly working out.

[Laughter]

And we are doing stretching exercises. We do a lot of yoga.

[Video: Four people attempt crow pose in yoga as another looks on, mountains are visible in the background; Audio: Inspirational music continues]

And so we obviously have to do bird poses, so that’s a crow, they’re doing a crow pose.

[Video: Two people taking down a mist nets in the snow; Audio: Inspirational music continues]

And some days you wake up in the morning and our mist nets are covered in snow, and we have to go out and take those mist nets down.

[Photo: Person removing a gray-hooded warbler from a mist net]

So when it’s not, when it’s not snowing, when it’s, when it’s, when we are actually working we catch mist, we catch birds using mist nets like these. Uh that’s one of my technicians taking out a gray-hooded warbler.

[Photo: Sahas’ hands holding a small bird with one wing stretched out]

and I’m actually going to show you how we measure, we get hemoglobin samples.

[Video: From previous photo, Sahas pricks the inside of the wing with a needle, collects blood with a flat microcuvette vial, then collects additional blood with a capillary tube; Audio: Birds songs]

So I make a small incision in the bird using a needle and then use what is called a microcuvette to take a small blood sample. Uh and I stick that thing in a small machine that gives me the hemoglobin concentration reading. Uh then I use um a capillary tube to draw blood to do hematocrit, uh hematocrit estimations. Um…

[Photo: Tree-covered mountains with clouds low over them and a blue sky]

so you might be thinking that um

[Video: From previous photo, clouds moving through the mountains; Audio: Inaudible talking and bird songs]

I’m really, really happy when I’m in the mountains, right, when there are clouds rolling by, and um you can,

[Audio: Five popping sounds of volume being turned up, followed by shrike and laughingthrush singing, then two more popping sounds]

that’s a shrike and laughingthrush singing, but after a point of time that becomes old.

What’s really, really fun is when

[Video: Camera pans across mountains, then cuts to another view of the mountains with lots of vegetation and pans to group of four people sitting on the grass with a loud humming noise in the background]

you’re making, you hear the sound of [inaudible] and that’s music to my ears. That’s my, that’s my, uh centrifuge running and that means I caught birds and am collecting data.

[Laughter]

Okay, so let’s go back to the predictions.

[Slide text: Predictions]

Uh, I had three basic predictions. The first one is that

[Slide text: Predictions 1. Hemoglobin increases along a species’ elevational distribution; Graph: Hemoglobin~Elevation showing an increase in hemoglobin with increased elevation]

hemoglobin concentration within a species across its elevational distribution increases with elevation. Okay. The second one is that

[Slide text: Predictions 1. Hemoglobin increases along a species’ elevational distribution 2. Species showing elevational migration show high hematocrit with high hemoglobin: Lowlander response; Graph: Hemoglobin~Elevation showing an increase in hemoglobin with increased elevation; Image: Drawing of a robin]

Hillary robins will show a lowlander response, and hence will show high hemoglobin concentration with a correspondingly high hematocrit. Okay, or volume of RBCs. The third

[Slide text: Predictions 1. Hemoglobin increases along a species’ elevational distribution 2. Species showing elevational migration show high hematocrit with high hemoglobin: Lowlander response 3. Resident species show weak correlation between hemoglobin and hematocrit: Highlander response; Graph: Hemoglobin~Elevation showing an increase in hemoglobin with increased elevation; Images: Drawings of a robin and a bushtit]

prediction was that Tenzing bushtits will show hemoglobin concentration and hematocrit that are not correlated with one another. And which will be a sign of the highlander response.

[Slide text: 1. Hemoglobin increases along a species elevational distribution; Graphs: Hemoglobin concentration by Elevation for six species (GBT, BTT, GHW, BLW, CCLT, and VLT); Images: Drawings of the six species]

So let’s see some results. Uh my first prediction was held true. Whether the birds were Tenzing bushtits or Hillary robins like this variegated laughingthrush the hemoglobin concentration within a species across its elevation range increased, which means that individuals of the same species at the lowest elevational distribution had low hemoglobin concentration at the highest elevational distribution, had really, really high hemoglobin concentration.

[Slide text: At elevational replacement, the lower species will show higher hemoglobin; Graph: Hemoglobin concentration by Elevation for white-throated laughingthrush and variegated laughingthrush, showing increasing hemoglobin with increasing elevation and the lower elevation species having higher hemoglobin concentration at the elevation where both birds live; Images: Drawings of the two species]

So a corollary to that is that as, as I have shown you before, species replace each other along the elevational gradient, right. So what we can sort of predict is that um

[Slide text: Physiological stress at upper limit; Image: Simple line drawing of a mountain with different colored bird silhouettes at various heights up the mountain with lines separating them, with the line below the red bird labeled “Lower Limit” and the line above it labeled “Upper Limit”]

at their upper limit the low elevation species should have a higher hemoglobin concentration, right. So um

here this is a white-throated laughingthrush that goes from fifteen, fifteen hundred to twenty-four hundred meters. At its elevational upper limit it will have a higher hemoglobin concentration than this variegated laughingthrush that replaces the white-throated laughingthrush.

Does that make sense? It’s a little unintuitive, but um. So um

we are the first to sort of

[Slide text: At elevational replacement, the lower species will show higher hemoglobin; Graph: Hemoglobin by species for Garrulax albogularis, Garrulax erythrocephalus, and Garrulax variegatus showing G. albogularis with highest hemoglobin; Images: Drawings of the three species]

show that in multiple species. So this is, we can show this with laughingthrushes and uh with

[Slide text: At elevational replacement, the lower species will show higher hemoglobin; Graph: Hemoglobin during winter and summer for cinereous tit and green-backed tit with highest hemoglobin in cinereous tit in winter; Images: Drawings of the two species]

chickadees. So these are cinereous tits and green-backed tits and across the year the low, low elevation cinereous tit has a higher hemoglobin concentration than the high elevation green-backed tit.

[Slide text: 2. Species showing elevational movement show high hemoglobin with high hematocrit; Graph: Hemoglobin versus hematocrit showing a strong correlation; Image: Drawing of robin]

Uh my second prediction was that Hillary robins will have a really strong correlation between hemoglobin concentration and hematocrit um and we

[Slide text: 2. Species showing elevational movement show high hemoglobin with high hematocrit; Graph: Hemoglobin versus hematocrit with many data points in several colors showing a correlation, r= 0.648; Image: Drawing of robin]

sort of see that uh with, with multiple species. So here each color is a different species. So many species from different families show the same reaction to hypoxia. If they are elevation migrants they show a really tight correlation between hemoglobin and hematocrit.

[Slide text: Resident species show weak correlation between hemoglobin and hematocrit; Graph: Hemoglobin versus hematocrit with several data points showing a much weaker correlation; Image: Drawing of bushtit]

As opposed to Tenzing bushtits, which I predicted to have a, a, a relationship like that.

[Slide text: Resident species show weak correlation between hemoglobin and hematocrit; Graph: Hemoglobin versus hematocrit with many data points in several colors showing a weak correlation, r= 0.160; Image: Drawing of bushtit]

And the real data also showed the same thing. So Tenzing bushtits or resident birds don’t have a strong correlation between hemoglobin and hematocrit.

[Slide text: What other life history traits drive hemoglobin? Range size, Range position, Elevation, Mass, Upper limit, Lower limit; Photo: Man holding a blue-throated barbet]

So then I sort of decided to throw a slightly more, slightly more complicated statistics at it and did what is called linear mixed modeling um approach.

[Slide text: What best predicts hemoglobin across species? (Hb~X+(1∣Species), N= 178, Species=15

Model Delta weight

Hct+EM+Hct*EM 0 0.994

Hct+Weight+Hct*Weight 10.18 0.006

Hct+Range+Hct*Range 22.56 0

Hct+Range Pos. +Hct*Range Pos. 23.12 0

Hct+Upper.limit+Hct*Upper.limit 23.29 0

Hct+Elevation+Hct*Elevation 27.34 0

Global Model 53.18 0

Range.Pos.+Elevation+Rang.Pos.*Elevation 55.48 0

Range+Upper.limit+Range*Upper.limit 59.69 0

Elevation+Upper.limit+Elevation*Upper.limit 62.2 0]

And I’m not going to going to get in the details but basically what it says

[Slide text: What best predicts hemoglobin across species? Hemoglobin~hematocrit + Elevational Migrant + hematocrit*Elevational Migrant + (1∣Species); Images: Drawings of Tenzing bushtit and Hillary Robin]

is that uh hemoglobin concentration is driven by the hematocrit of the bird, and whether the bird is a elevational migrant or not. Which means it, whether the bird is a Tenzing bushtit or a Hillary robin greatly drives the hemoglobin concentration of a bird.

Okay so

[Slide text: Does physiology affect competition?]

why is this important? Right, why why should we care about physiology of birds? Other than just from a scientific point of view. So one, one of the important things is

[Slide text: Physiological stress at upper limit; Image: Simple line drawing of a mountain with different colored bird silhouettes at various heights up the mountain with lines separating them]

we really don’t know how physiology affects other other interactions like competition, right. So we can say that at its elevational upper limit, a species might be physiologically stressed. But does that sort of translate into how competitive it is to other species?

[Slide text: Does physiology affect competition?]

Right, so I’m going to show you a small video of um, that Shailee Shah another uh undergrad here took of a green-backed tit and a cinereous tit at a feeder in the Himalaya. So you might actually hear the sights and sounds of a Himalayan village.

[Video (Macaulay Library ML 515553): Green-backed tit eating at a feeder, which is a tree branch covered in seeds. A cinereous tit is perched on a branch above and to the side of the green-backed tit. The cinereous tit flies out of view. The cinereous tit flies back to the branch and slowly gets closer to the feeder, and the green-backed tit. It lands on another part of the feeder, but the green-backed tit chases it away quickly; Audio: Sounds of people in the village and birds singing]

So that’s a green-backed tit um. Let me see if I do that, yeah. So that’s a green-backed tit feeding on a feeder, and that’s a cinereous tit, so cinereous tit is the physiologically stressed underdog, and the green-backed tit is the, um, is the overlord of the feeder right now. And you’re going to see what happens when a cinereous tit tries to steal some food from the uh green-backed tit.

So cinereous tit makes its way slowly. Yeah. So the green-backed tit does not like it, and cinereous tits are complete pushovers at their elevational upper limit because they get outcompeted, potentially because they are physiologically stressed and can’t, can’t be good competitors.

Um. The other reason. Hold on, let me go back my presentation.

[Slide text: Does physiology affect competition?]

The other reason why studying hypoxia physiology is really important

[Slide text: Where the wild birds are

Distribution of the world’s bird species: based on overlying the breeding and wintering ranges of all known bird species, Birdlife International; Image: Map of the world with darker colors representing higher number of bird species present in an area, showing highest concentrations of birds in northern South America, central Africa, and parts of southern Asia including the Himalayas]

is that if you plot all the, if all the species of birds on a world map, you can actually see the outlines of all the major mountain systems. So you can actually see the Himalayas, the Andes, the Central African Rift Valley mountains.

They all light up because mountains around the world are packed with bird species. And we don’t know anything about how these birds respond to hypoxia. Right. So one of our major predictions is that with climate change species are going to move up slope as the temperatures rise.

But if they can’t cope with hypoxia they might not be able to move up slope, as, as readily as we thought they would.

[Photo: Mud with tracks and markings in it and grass]

and the last reason is that we are losing birds really, really quickly. So this is a photo from my field site. In a square foot of mud um you have a pugmark of a leopard, tire tracks from a car, these are the hoof prints of a cow, and someone had scribbled “Unu I hate you”. And all this happened in one square foot of mud.

So around the world on mountains there’s a lot of habitat changes that are happening. And we are losing a lot of really, really cool birds, or in, many cool birds are getting endangered because of habitat loss. And we might lose a lot of those species before uh we even know, how, know about like, know anything about them completely.

[Slide text: Thanks Cornell University Department of Ecology and Evolutionary Biology, The Cornell Lab of Ornithology, Atkinson Center for a Sustainable Future, Sigma Xi The Scientific Research Society, Wildlife Institute of India, The Explorers Club, Forest Department Uttarakhand, Indian Institute of Science Centre for Ecological Studies, Images HBW, Shailee Shaw, Soham Dixit, Pratik Joshi]

So with that I would like to thank my, my several uh funding agencies

[Photos: Various photos of field assistants both working and playing]

and my hard-working field assistants. Uh and leave you with

[Photos: Head portraits of sixteen Himalayan bird species]

a few photos of Himalayan birds. Thank you.

[Applause]

Are there questions? Yes?

[Audience question]

[Sahas] Mhmm.

[Audience question]

[Sahas] Right.

[Audience question]

[Sahas] Right. So. Yeah the question is if, if, if tropical mountains have more species. And yes, the answer is yes. Tropical mountains are sort of have disproportionately more species than other mountains around the world, yeah.

Yes?

[Audience] Do you have the sense of whether there are behavioral changes that they can make as well to cope with hypoxia, in terms of like changing activity level and things like that?

[Sahas] Um… nothing like that is known. So we know some birds will go into torpor at night, to sort of reduce body, bodily functions. Uh but there is very little they can do to sort of overcome hypoxia behaviorally.

Yes?

[Audience question]

[Sahas] Yeah, so they, they might have, just talking from a sort of a blood perspective they could have smaller, so this has been seen in deer mice in the Rockies. They have smaller erythrocytes, so they have smaller RBCs, which increases the total surface area to volume ratio for binding with oxygen. Uh but they might also have, since you’re a physiologist, I can tell you they also have, they might also have what is called MCHC, right.

So they have more hemoglobin packed into each red blood cell than your normal red blood cells. So those are two sort of blood-related ones. But then there could be, they could have bigger air sacs or I don’t know. There could be other mechanisms also.

Yes?

[Audience question]

[Sahas] Mhmm. Mhmm. Uh… I don’t. Right, that’s a great question actually. I, I don’t know if there is any age, if they sort of sort themselves out age-wise. Um but what I can say is that the nesting season is longer in the lower elevations than at the highest elevations. Uh because it’s, even, a span of a thousand meters on a mountain makes a big difference.

You can potentially get 15 or 20 days more uh to nest in the lower elevations as compared to high elevations.

Yes?

[Audience question]

[Sahas] No, but if you, if you can come, if you can measure the size of the red blood cell, and if you have the hemoglobin concentration of the bird then you can get at what that is pretty well.

[Audience question]

[Sahas] Not in the Himalayan birds because um, sort, to measure that you need to get the blood under a microscope with a camera within 24 hours. And that’s something that I can’t do in the Himalayas.

Yeah?

[Audience] Do you expect there’s a difference in the incubation periods because oxygen levels are fairly important in incubation periods?

[Sahas] Yeah, so it’s been shown with ptarmigans uh in the Rockies that, so ptarmigan eggs have a, bigger pores and the incubation period is longer in ptarmigans. I don’t know if people have looked at incubation periods in songbirds in the Himalayas, or actually anywhere. But it has been shown with birds in the Rockies, yes.

Oh. Well, thank you so much.

[Applause]

[Lisa] So last up tonight we have Conor Taff. Conor is a postdoctoral associate here at the Lab. And before coming to Cornell in 2015 he completed an NSF-funded PhD and USDA-funded postdoctoral research at University of California- Davis.

Conor has been studying wild birds for over 10 years, and during that time his work has addressed questions about breeding biology, life history trade-offs, sexual signal elevation, epidemiology, and movement ecology in common yellowthroats, greater sage-grouse, and American crows.

Conor’s also the recipient of multiple awards, including the Cooper Ornithological Society Young Professional Award, and the UC Davis Martin Love Award for best dissertation in any area of ecology or evolution at UC Davis. So we’re lucky to have him, welcome Conor.

[Conor] Thanks.

[Applause]

[Slide text: A Warbler Soap Opera: Color, Song, Sex, and Senescence in the Common Yellowthroat

Conor Taff, Postdoctoral Associate, Cornell Lab of Ornithology & Dept. of Evolution & Ecology, Cornell Lab of Ornithology Monday Night Seminar; Photo: Male common yellowthroat perched on a branch]

[Conor] All right, so thanks for giving me the opportunity to talk to you tonight. Um so I want to start by showing you this picture

[Photos: Various colorful and striking animals including a peacock, a fairywren, a bird of paradise, a spider, an anole, fish, and more]

and one of the things that I find most fascinating about studying wild animals, and that got me excited about pursuing this as a career is the amazing degree of diversity that you see in signaling traits across a variety of species.

And so that’s true certainly in visual traits like what we’re looking at here, like dewlaps on lizards, and stalk-eyed fly antennas, and of course in plumage patches in birds.

And understanding how and why these elaborate traits have come to be has been a real puzzle for biologists for a long time. Um so as many of you probably know, Darwin proposed, um about 150 years ago the mechanism of natural selection as the main driver of evolution.

But he himself was really puzzled by how these elaborate traits that seem to serve no utilitarian purpose could evolve under natural selection. And he thought a lot after his first book came out, um about how we could see this evolution. And was so puzzled by it that he wrote to

[Slide text: “…small trifling particulars of structure often make me very uncomfortable. The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” -April 3rd 1860 letter to Asa Gray; Photos: Charles Darwin seated, and peacock feathers up close]

his friend Asa Gray in a letter in 1860 that “small trifling particulars of structure often make me very uncomfortable. The sight of a feather in a peacock’s tail, whenever I gaze at it makes me sick!”

[Laughter]

And a lot of his career was spent thinking about these sexually selected traits, and the way that he eventually resolved this paradox to his own satisfaction was by proposing a special type of natural selection that he called sexual selection.

Um and basically he argued that in addition to competing to survive and reproduce, animals might compete for access to mating opportunities. And there are two main ways he thought this could happen.

One being intrasexual selection, where members of one sex compete with each other for access to the opposite sex. So things like bighorn sheep where males butt heads and only the most dominant male can mate with the harem.

And the other being intersexual selection, where members of one sex have a mating preference based on some aspect of the signaling traits of the opposite sex. And this is where he thought you could get the evolution of these elaborate plumage patches when females, and we often think about females although there are some species where these sex roles are reversed.

Um so typically females exert some kind of mating preference, and that over many generations lead to, leads to the evolution of these truly elaborate um traits that I showed you in the last slide.

And so it’s relatively easy to imagine in birds how this might produce those signals in some species, so things like

[Photo: Male greater sage-grouse displaying]

greater sage-grouse where you have a lekking mating system. Um so these are the, the birds that my advisor worked on, and I did a couple field seasons on them. And they have these amazing mating system where every breeding season the males gather on a lek.

Um they perform this really complex behavioral display with vocalizations using these inflated air sacs. And they also have this elaborate plumage with plumes on top, and this great spiky tail in the back. And in a typical sage-grouse lek with a hundred displaying males you might only have three or four males who successfully mate the entire season.

So females are coming and visiting the lek, and they basically have free choice of any male that they want to mate with. Um and the most successful male might mate 40 or 50 times.

So you can imagine that if the degree of elaboration of this plumage is related to the choices that these females are making, you can get really strong selection leading to more and more elaborate plumage.

But the reality for a lot of birds turns out to be that about

[Photo: Male common yellowthroat with leg bands perched on a branch]

ninety percent of the birds in the world are socially monogamous. So they don’t have this elaborate lek mating system. Instead like a lot of the birds around here, they’re territorial where males have a single territory. They often have one or maybe two females who settle on that territory, and so you don’t have this apparent, um this apparently very large reproductive skew where a few males are monopolizing all the matings.

And so it was a puzzle for a long time to understand how in these socially monogamous species you could still get fairly elaborate plumage. And so this is the bird that, that I did my dissertation on, the common yellowthroat, that I’ve been working on for over 10 years now. Um they’re maybe not quite as elaborate as the sage-grouse on the last slide, but they do have this really nice striking plumage.

So the males have this black facial mask that the females don’t have at all. And they also have this very bright yellow bib that extends down their whole front in some birds. And females do have a version of the yellow bib, but it’s smaller and duller.

And so um, it, about 30 years ago someone, the key insight in understanding how we could get sexual selection um acting on plumage in these socially monogamous species occurred about 30 years ago when it became possible to apply genetic paternity tests to wild birds.

And it turned out that even though we have these socially monogamous mating systems in most cases the genetic mating system is actually not monogamous. So even though you have a territorial male and a female defending a territory together, and provisioning the young together some of the nestlings in the nest of most songbird species are actually sired by males on neighboring territories.

And in some species this can be um, a really extreme. So in some socially monogamous species you might have actually fifty or sixty percent of the nestlings sired by males on nearby territories.

And so in yellowthroats the kind of main questions that we’ve been addressing over the the course of this research program are

[Slide text: What are signals used for? Photo: Male common yellowthroat with leg bands perched on a branch]

What are these signals actually use for? So are they related to reproductive success? Are females paying attention to them?

[Slide text: What are signals used for? What information is conveyed by signals? Photo: Male common yellowthroat with leg bands perched on a branch]

What information is conveyed by signals? So if females are paying attention is there a reason? When they pay attention to these signals in mate choice are they getting information about the underlying physiology of those males?

[Slide text: What are signals used for? What information is conveyed by signals? How is honesty maintained? Photo: Male common yellowthroat with leg bands perched on a branch]

And how is honesty maintained? So the kind of flip side to that is are their physiological constraints that prevent males from cheating? If it’s good to be bright and have a big yellow bright bib, why don’t all males have big yellow bright bibs? Is there something that’s creating variation in the population.

[Image: Map of North America showing the breeding range across most of the United States and much of Canada, resident populations in some of the southern United States, California, and parts of Mexico, and wintering in the rest of Mexico and the Caribbean]

And so before I go into some of the results that we found I just want to give you a little bit of natural history on common yellowthroats. So as their name implies they are really common. They’re found over pretty much all of North America. So the breeding range here in pink is pretty much over the entire northern United States and Canada. Um they also have some resident populations that don’t migrate in Florida and California.

Um one of the things that I really like about yellowthroats is that they’re a bird that is super common, they’re very abundant, but a lot of people who aren’t birders have actually never seen one. In about a month if you go out with your car windows, I think many of you who are listening to this probably have seen yellowthroats.

But if you go out driving around pretty much any of the areas in their range with your windows down and you’re near a swamp, you’ll hear them singing from the swamp, so they’re really prolific.

[Photo: Marshy meadow with a stream running through it in front of trees, over the previous map]

This is what the typical habitat looks like. This is a picture of one of my field sites so this is a series of beaver meadows that extend up an old river.

[Animation: Green star added to previous map over Saratoga Springs, New York]

And the main field site that I’ve worked at is here in Saratoga Springs, New York, so it’s only a couple hours away from here. Pretty similar to the habitat we have

[Photos: Various photos of technicians drawing blood, measuring, and banding common yellowthroats]

right around Ithaca.

So each field season, um we go out and on the territories that we’re monitoring we catch all the birds in mist nets, so you can see us taking a bird out of a mist net here. We catch all the adult males and females and take your standard kind of morphological measurements of the body size of these birds, we put these colored plastic leg bands on.

Um we put a unique combination on each bird so that we can then go out with binoculars and identify them for behavioral observations later. And we take blood samples from all the adults and nestlings in the population so that we can do the genetic paternity analysis. And also for some physiological measures looking at the blood.

[Photos: Yellowthroat nests, including one with four eggs and one nestling and another with an adult female on it, and a group of nestlings in a person’s hand]

But the vast majority of our field season is actually spent tromping through swamps in knee-high boots trying to find these nests. Um so the females in particular are incredibly cryptic. They’re in this dense, marshy habitat, and here’s a female setting on her nest here, so you can see she doesn’t have the black facial mask and her back in particular just blends in perfectly with the um, vegetation that’s in these swamps.

And so this bottom picture here is showing you a yellowthroat nest from about a foot away. So you can imagine that these, they almost, when they’re building their nests they’re almost like mice. They get a strip of grass and they run along the ground to their nest, and run along the ground away from their nest. Um so it’s very hard to follow them.

They’re very skittish if you get too close to the nest. And they have high predation rates, so we end up having to find the nest over and over again.

When we do find them, um we monitor the nest every day until they hatch. So this is a yellowthroat nestling that’s just a couple of hours old. And then when the nestlings are five days old, which they are in this bottom picture here, we go back and put bands on them and take blood samples from the nestlings as well.

And so with the help of a lot of people over many years

[Slide text: Mask Size; Photos: Two photos of male yellowthroats being held by the beak and against a checkered mat]

we’ve built up this um, large data set. Okay, so before that slide. We, we also are interested in a couple different plumage measures, and I just want to show you what those look like here.

So first I mentioned that they, males have this black facial mask. It turns out that this varies a lot between males. So these are two males in the population, one with a large mask, and one with a small mask. And we photograph all the birds against these standardized grid backgrounds. And then we can use a computer program to measure the area of those plumage patches later on.

[Slide text: Mask Size, Bib Size; Photos: Two photos of male yellowthroats being held by the beak and with one side of their bodies against a checkered mat, and two photos of male yellowthroats held with backs flat against the checkered mat and beaks stretched up]

They also vary a lot in bib, so again this male on the left has a large bib, um this male on the right has a small bib. We measure the area of the bib as well. And for the bib we also measure the variation in the quality of the color um that’s in the feathers.

And to do that we pluck a few feathers from the center of the bib, and use something called reflectance spectrophotometry

[Slide text: Mask Size, Bib Size, Bib Coloration; Photos: Two photos of male yellowthroats being held by the beak and with one side of their bodies against a checkered mat, and two photos of male yellowthroats held with backs flat against the checkered mat and beaks stretched up; Graph: % Reflectance by Wavelength (nm) with a peak at around 365 nm, lowest reflectance at about 450 nm, and highest at about 525 nm and above]

to generate these reflectance spectra. And the x-axis here is wavelengths in the visible spectrum. The y-axis is the percent reflectance, so that’s how much reflectance is at that wavelength. The yellowthroats have this typ—this is a typical profile for a male, where they have a peak down here in the UV range, which we actually can’t see at all, but birds because they have a fourth color cone can see. So presumably these patches actually look quite different to a female yellowthroat than they do to us.

But we can quantify the variation in that yellow coloration. And they have a dip in the middle wavelengths, and then another big peak in the yellow range, which is what we see when we look at these birds. So they appear yellow to us.

[Slide text: Single perch song repeated all breeding season.; Photo: Banded male yellowthroat perched on a branch and singing; Image: Spectrogram of yellowthroat song]

They also have a single song that they repeat over and over again throughout the breeding season, and so they don’t have a repertoire, but each male has their own song

[Audio: Chipping sound of male yellowthroat]

Um so these are the chips, it’s kind of a contact chip.

[Audio: Male yellowthroat song]

And that’s the yellowthroat song. So it’s witchety-witchety-witchety. Um they’re really prolific singers, and they’re the most common singers in this habitat. I’ll come back to that in a minute.

[Photo: Banded male yellowthroat perched on a branch]

So here’s the slide I meant to be at before. Um, so over the the last 10 years with the help of a lot of field assistants, and a lot of effort we’ve built up this big data set from our local field site where we’ve followed

[Slide text: > 200 males > 150 females > 500 nests > 800 nestlings 100% paternity assignment 18% extra pair young; Photo: Banded male yellowthroat perched on a branch]

a little over 200 males, about 150 females, um we’ve found 500 of those nests, which I think is probably the major accomplishment of this entire project, and sampled about 800 nestlings.

And one of the nice features of our field site is we have these swamps that are surrounded by dry woodland on all sides, so we don’t have any neighboring territories of yellowthroats that we’re not following. So we’re actually able to assign genetic paternity to all of those eight hundred nestlings. And it turns out that eighteen percent of them are extrapair young. Um so we have this potential mechanism for sexual selection through extrapair mating success in addition to within-pair mating success.

[Slide text: The Basics

Plumage size & coloration related to:

Mitchell et al. Animal Behaviour. 2007 Dunn et al. J Avian Biology. 2008 Freeman-Gallant et al. Evolution. 2010 Dunn et al. Functional Ecology. 2010 Freeman-Gallant et al. Biology Letters. 2011 Taff et al. Animal Behaviour. 2011 Taff et al. Wilson J Ornithology. 2012 Taff et al. Animal Behaviour. 2012 Taff et al. J. Evolutionary Biology. 2013 Freeman-Gallant et al. J. Evolutionary Biology. 2014 Taff et al. Hormones & Behavior. 2014 Taff et al. Proceedings Royal Soc. B. 2014 Whittingham et al. Molecular Ecology. 2015 Taff et al. Ethology. 2016; Photo: Banded male yellowthroat perched on a branch in a slightly different position]

and I’ll just give you a quick rundown of kind of the, the early results from our project. Um, the basic take away is that we know that plumage size and coloration are related to a lot of things that seem to be important for mating success. And particularly, um bib coloration and bib size seem to be more important than mask in our population.

So different aspects of bib size and coloration are related

[Slide text: The Basics

Plumage size & coloration related to: Male dominance Female preferences Extrapair mating success Within-pair mating success Survivorship …and more

to, to male dominance and female preferences when we do aviary trials. Um in our natural population both extrapair mating success and within-pair mating success are related to bib coloration. And there’s also relationships with survivorship, so um, um plumage coloration predicts survivorship over the winter. And so you can imagine that a female paying attention to bib coloration might be interested in survivorship, um to the extent that that’s a heritable trait that their offspring will then get.

Um similarly for song, um

[Slide text: The Basics

Plumage size & coloration related to: Male dominance Female preferences Extrapair mating success Within-pair mating success Survivorship …and more

Song performance is related to: Extrapair reproductive success Survival …and more

so we haven’t done quite as much work on song, um but we do know that extrapair reproductive success is related to song performance. So males that sing more consistently, um are able to sire more extrapair young. And again there are relationships with survival.

So it seems like there’s a potential for selection driving the evolution of some of these traits, um in our system.

[Slide text: Communication Networks; Images: Cartoon renderings of seven pairs of yellowthroats with two-way arrows between the male and female. The males all have large bibs. Two additional males are not paired with females. One has a small bib.]

Um, but we’ve been more, I want to talk a little bit more detail, in a little bit more detail about some work we’ve been doing more recently. And first I want to talk about a project that we’ve been doing to try to look at communication in networks in our population.

So the early work that we’ve done has all really focused on what was going on between a male and a female on their home territory. Um but yellowthroats, like most songbirds, or a lot of songbirds around here, have this network of territories where at our field site you have these pairs of interacting males and females. So the male on the left here, female without the mask on the right. So you can think of this as a territorial pair.

We also have some males in our population who come, claim a territory, sing all season and never attract a female. Those tend to be the young males, but we do

[Slide text: Communication Networks; Images: Cartoon renderings of seven pairs of yellowthroats with two-way black arrows between the male and female. The males all have large bibs. Two additional males are not paired with females. One has a small bib. Two way blue arrows connect various pairs with each other and with the unpaired males]

put them in here as well. Um when you have this network of territories you have a potential for communication to occur not just between a male and a female on their own territory, but at this larger network level. And that’s maybe not as true for something like plumage that has to be assessed at close range, but for song that carries a long distance, there’s a potential to both signal to neighbors, and to listen to what’s going on on neighboring territories.

And so we’ve been interested in trying to understand first of all whether males when they’re making their singing decisions are even paying attention to the neighborhood context, and whether they’re changing their singing to match kind of subtle changes in what’s going on in the entire neighborhood rather than just on their own territory.

[Slide text: Remote Monitoring of Song Behavior]

And so we’ve been doing that using remote monitoring of singing behavior so

[Slide text: Remote Monitoring of Song Behavior; Photos: Song recording device by itself and song recording device on a snag in the marsh]

we use these great waterproof and weatherproof song recording devices um that record to SD memory cards. They can be set to record on a fixed schedule. So we can record many territories at a time, and for many days in a row. Um and get total song production from all of the males in our population.

Um as I said males don’t have a song repertoire, so we’re actually able to use recordings that we made using a microphone of each male to match up to these and identify each of our focal males um to see how many times they were singing.

[Photo: Grassy marsh with stream, evergreen trees around the marsh, and a hill in the background]

Um and I just want to give you a snippet of what this would sound like. So if you were at one of my field sites in upstate New York

[Photo: Grassy marsh with stream, evergreen trees around the marsh, and a hill in the background; Image: Spectrogram of spring peeper call; Photo: Spring peeper with throat sac enlarged while calling; Audio: Spring peepers calling]

in early May um just before dawn you hear the spring peepers going here. And before the spring peepers have even stopped, you hear the first yellowthroat come in.

[Photo: Grassy marsh with stream, evergreen trees around the marsh, and a hill in the background; Animation: Spectrogram moving through sounds of the marsh, including spring peeper, yellowthroat, and gray catbird; Photos: Spring peeper with throat sac enlarged while calling, male yellowthroat, and gray catbird; Audio: Spring peepers calling, and yellowthroat and gray catbird singing]

So you can see in the spectrogram here yellowthroat vocalization. Um these recordings do pick up a lot of other birds, things like gray catbirds, which are really amazing singers, but are actually the most annoying birds in these recordings because they just sing incessantly, and make it hard for us to measure what we want.

[Photo: Grassy marsh with stream, evergreen trees around the marsh, and a hill in the background; Animation: Spectrogram moving through sounds of the marsh, including veery and song sparrow; Photos: Spring peeper with throat sac enlarged while calling, male yellowthroat, gray catbird, veery, and song sparrow; Audio: Veery, song sparrow, and yellowthroats singing, and yellowthroat territorial rattle]

A veery here, that’s one of my favorites singing from the edge of the swamp, and a song sparrow. Um but in these habitats and in these recordings it’s quite amazing actually the yellowthroats are by far the most prolific singers.

And so this, this is an early-season recording, you actually can hear three males counter-singing at the edges of their territory here. And so they’re probably setting up the territory boundaries early in the season. And at the end here one male intrudes into the focal male’s territory, and you’ll hear a rattle, which you can see here.

So that’s the most aggressive yellowthroat vocalization. That’s the, that focal male chasing that intruder back out of the territory.

And so these, these recordings can make these great soundscape audio files that if anybody is interested in downloading some to listen to while you’re going to sleep I have thousands of hours of these recordings.

[Laughter]

Um but you can also pull a lot of interesting data out of them. So with some um signal processing, um using a computer program and a lot of manual checking, we can actually pull out the total song production for all the males in our population. And we have really detailed census data from all of these years, so we know exactly what was going on in every territory. And we can look at how males are actually changing their singing as the fertility status of neighboring females changes.

We know, and these these recordings confirm, that males decrease their singing a lot when their own female is fertile, presumably because they’re following the female around, trying to mate with her and stop other males for mating with her. But we haven’t known before this what males are doing in response to neighboring females. And it turns out, I’ll just jump to the results here.

[Slide text: Influence of Neighborhood Fertility, Taff et al. 2014. Proc Roy Soc B; Graph: Daytime Songs versus Fertile Females in 400m showing increase in songs with increase in fertile females]

Um, that on the y-axis here you’re looking at the total amount of song production, the x-axis is the number of fertile females within 400 meters. And we know from some previous work that 400 meters is about the maximum distance that males will travel to sire extrapair young.

So for each additional female within 400 meters, males are singing about ten to twenty percent more each day. And these birds weigh 10 grams, so they’re about the size of two U.S. quarters, about the weight of two U.S. quarters. And they’re singing in some of these recordings up to 2,000 songs in a day.

So it might not seem like a huge increase, but ten to twenty percent increase for such a small bird that’s already singing a lot and might have three or four fertile females in the neighborhood, um is a pretty substantial increase in singing effort.

And I think one of the things that I’m most excited about with these results is just that it suggests that these males are um, you know these small songbirds are aware to some extent of what’s going on not just on their own territory, but on these neighboring territories up to 400 meters away, and actually responding to that in a way that seems to make sense adaptively.

Um we don’t know exactly how males are, how males are getting that information. One possibility that’s intriguing is that they’re actually paying attention to how much their rivals are singing, and as their rivals decrease their singing the vocal males are actually ramping their singing up because they know that there’s a focal, a fertile female on that territory.

[Slide text: Cellular Processes Influencing Signal Production and Senescence]

Um another major focus of our work, and I just want to touch on this briefly, has been trying to link physiological mechanisms to the expression of signals that we see and ask whether physiology in some sense might be constraining the expression of um ornamental traits.

[Slide text: Cellular Processes Influencing Signal Production and Senescence Telomere Erosion: What We Lose With Age

As cells divide over time… telomeres shorten, and eventually cell division stops; Image: Graphic showing telomere (a protective covering) at the end of a chromosome becoming shorter then disappearing over time after multiple cell divisions]

And so we’ve done this in a number of different ways. I just want to mention one here as an example that we’ve done recently. And that’s that we’ve looked at telomere shortening with respect to ornamentation. So telomeres are these repeated base-pair sequences that cap the ends of eukaryotic chromosomes. And they shorten throughout life as cells divide.

They’ve received a lot of attention actually in human medical literature. They’re implicated in a lot of cancer formation, and a lot of cancer biologists work on telomere erosion.

They’re thought to be related to the aging process. And so we’ve measured for our birds where we have consecutive years of sampling, we’ve measured telomere lengths between years, and ornamentation between years.

[Slide text: Telomere shortening; Graph: Telomere RQ by Year N Color PC1, with Year N, P = 0.02, Year N+1, P < 0.0001, Year N+2, P = 0.05]

And it turns out that, um the y-axis here you’re now looking at the absolute telomere length. Um the x-axis is coloration. And it turns out that coloration in a male’s first year breeding predicts their telomere length during that breeding season, and during the subsequent two breeding seasons.

[Slide text: Telomere shortening; Graphs: Telomere RQ by Year N Color PC1 with Year N, P = 0.02, Year N+1, P < 0.0001, Year N+2, P = 0.05, and ∆ TRQ Year N to N+1 by Year N Color PC1 with P < 0.001]

And the change in telomere length between years is also predicted by coloration. So males that have bigger brighter yellow bibs have longer telomeres, and are losing telomeres at a slower rate.

So again this suggests to us that males paying attention, or females paying attention to ornamentation are potentially getting information about the underlying physiology of those mates.

[Slide text: Telomere shortening, Plumage coloration predicts both the length of telomere over the next 2+ years and also the rate of telomere loss between years.; Graphs: Telomere RQ by Year N Color PC1 with Year N, P = 0.02, Year N+1, P < 0.0001, Year N+2, P = 0.05, and ∆ TRQ Year N to N+1 by Year N Color PC1 with P < 0.001]

[Slide text: Where do our birds come from and fly to??]

Um and then the last thing that I want to talk about is something that I don’t really have results from yet, but I’m excited about we’ve been doing over the last couple years. I’m not really working actively on yellowthroats right now, but we have some side projects still continuing.

[Slide text: Where do our birds come from and fly to??; Image: Map of contiguous United States labeled “Stable Hydrogen Isotopes In Feathers” with Tap water isotope in different colors, showing it changes with location. Collection sites are also shown in many states]

And one of those is that we’ve been looking at, um. The isotopic signature in feathers to try to get a sense of where males are moving across the landscape. So everything that we’ve done so far has really been focused on this one field site in upstate New York. But we’re trying to scale this up to understand how movement across the landscape might influence the expression of signals that we see in our um breeding population.

[Slide text: Where do our birds come from and fly to?? Latitude where feathers were grown is related to coloration for young birds. Pattern is created by northward dispersal by some young birds.; Image: Map of contiguous United States labeled “Stable Hydrogen Isotopes In Feathers” with Tap water isotope in different colors, showing it changes with location. Collection sites are also shown in many states]

And there’s this nice feature of precipitation um that as you move northward up the, as you move northward in latitude the ratio of hydrogen to deuterium, the heavy isotopic form of hydrogen, changes predictably.

And because feathers are inert tissue once they’re grown that ratio is locked in. Um so when we sample feathers, those are feathers that were molted the previous September. We can put them in a mass spectrometer and look at this ratio and actually know where the birds, a fair approximation of where the birds are when they grew those feathers.

And it turns out that the latitude where feathers were grown is related to coloration in our birds among yearlings. And what seems to be driving this is that some birds in our population were hatched farther south from our site, and are actually dispersing up into our site as breeders. And so there’s potentially some interesting things going on here um with the ecological drivers of coloration um leading to variation in our field site.

And the flip side to that is that we’d also like to

[Slide text: Where do our birds come from and fly to?? Latitude where feathers were grown is related to coloration for young birds. Pattern is created by northward dispersal by some young birds.

Geolocators 20 Geolocators deployed in 2015. Fingers crossed for their safe return in 2016!; Image: Map of contiguous United States labeled “Stable Hydrogen Isotopes In Feathers” with Tap water isotope in different colors, showing it changes with location. Collection sites are also shown in many states; Photo: Banded male yellowthroat with a geolocator on his back being held in a person’s hand]

know about where our birds are spending the winter. And up until now we don’t have any information on where they’ve been going. Um despite the many, many years of people banding hundreds of thousands of birds um on the breeding grounds in North America, re-sighting those birds on the wintering grounds is vanishingly rare.

Um so we often don’t know, we know the yellowthroat range in the south, but we don’t know where our particular birds spend their winter. And yellowthroats as I said weigh the s—weigh about the weight of two U.S. Quarters, so until very recently it’s been impossible to put tracking devices on them.

But in the last couple of years it’s been, become possible to put these geolocators that lay, weigh less than half a gram on birds as small as yellowthroats. And so we actually put 20 of these out last year. And the way that these work is it’s basically just a very small battery, a memory card, and a light sensor. And it records the time of sunrise, and the length of daylight. Um and with this, those two pieces of information you can actually calculate latitude and longitude.

Um so we put 20 of those out last year, and in about six weeks, or actually may—right about now those birds, presuming they’re still alive, should be starting to think about migrating north. In about six weeks we should know if any of them return. We can catch those birds again, pull those off, and for the first time get information on where our birds are spending the winter.

[Slide text: Field & Lab Assistance: Joel Amidan, Brittany Berdy, Jon Betz, Courtney Clark, Jon DeCoste, Lindsey Duval, Julia Ersan, Sarah Fansler, Elaine Fong, Becki Fox, Megan Garfinkel, Evan Krasner, Iris Levin, Kate Littrell, Blake Massey, Dan Mitchell, Doug Morin, Marc Pedersen, Paige Reeves, Hayley Sacks, Jakob Schenker, David Steinberger, Ian Taff, Susan Tsang, Toshi Tsunekage, Stephanie Wein, Ben Yamane, Stephanie Zendejas Funding: UCD Grad Research Fellowship, NSF Pre-doctoral Fellowship, Animal Behavior Grad Group, UCD Grad Student’s Assoc., Explorer’s Club Exploration Fund Award, NSF DDIG, Francine A Bradley Award, SSE Rosemary Grant Award, Skidmore College, Cooper Ornithological Society, UCD Center for Population Biology, UCD Graduate Studies, UCD Dissertation Year Fellowship Collaborators and Advisors Gail Patricelli, Corey Freeman-Gallant, Peter Dunn, Linda Whittingham, John Wingfield, Ann Hedrick, Kara Belinsky, Mark Haussmann And more help from: Tom Hahn, Karen Kellogg, Richard McElreath, Andy Sih, UC Davis Grad Students, Marilyn Ramenofsky, Judy Stamps, Heather Watts, Mark Youndt; Images: Logos of various funding organizations; Photos: Various field assistants and collaborators and advisors]

Um and I just want to acknowledge that what I’ve talked about here is, represents a decade of work with a lot of collaborators. And so there’s a whole list of mostly um undergraduate field and lab assistants who have worked on this over the years. Funding sources that have paid for various parts of the project, and collaborators and advisors who helped me with various parts of it.

[Slide text: Conor Taff Postdoctoral Fellow, Lab of Ornithology & Ecology & Evolutionary Biology Dept.

Cornell University cct63@cornell.edu; Photos: Conor holding a male yellowthroat, and banded male yellowthroat perched on a branch]

And I’m happy to take some questions.

[Applause]

Yeah?

[Audience] I’m trying, having trouble reading your graph. Does it suggest that three is the ideal number of outside females uh to generate song? Because it looks like it drops off when you get to five or six.

[Conor] Yeah, it looks like it drops off, but. So the question was in the graph, the relationship between the number of fertile females and song production, why does it look like it drops off when you get up to five and six females? The answer really is just that there are very few instances where there were five or six fertile females. Um so those, the sample sizes for those two are very small. Yeah, so whether they would keep singing more if there were more fertile females we don’t know what the maximum is there.

Yeah?

[Audience] Is there a correlation between, on the amount of bib, on the bib size, the more there is in the visible light, does that correspond to an increase also in the, in the um UV?

[Conor] Yeah it does tend to be. So the way that the the feathers are actually grown, um it’s interesting. And we haven’t fully quantified this, but the, the feathers themselves if there’s no pigment deposited them, in them, are white. And so the actual, the elevation of that full reflectance curve has to do with how pure the white coloration is. That’s not a pigment it’s a structural color.

And then once you have that pure white feather, um as it’s growing they deposit carotenoids, which is the pigment that actually turns it yellow. And the the carotenoids are actually a subtractive pigment, so they pull that trough in the middle down. The more carotenoids you have the lower that trough goes.

So that initial shape um there is a correlation between the UV coloration and the yellow coloration. That kind of whole elevation of the shape is probably determined by the actual structure of the feathers rather than the pigments.

And it’s possible, I mean people, we haven’t done this with our birds but it’s possible to actually measure the coloration and then do a process where you pull all the pigmentation out, and then re-measure the white coloration, and get how much pigment was actually deposited there, and whether there’s variation in the base white color as well.

Yeah?

[Audience] Let me see if I can get this right, so. Um a lot of this, most of this was done in relation to the extrapair sexual bonding.

[Conor] Mhmm.

[Audience] Does that, is there a reason why, or I guess the question is, does any of this coloration um, advertising have anything to do with the original pairing, their social pairing.

[Conor] Yeah.

[Audience] Is there an issue there of attraction that’s important at that point?

[Conor] Yeah. So the, the question is whether, I was mainly talking about extrapair mating success, the question is whether there are relationships with within-pair mating as well? And there are some, particularly, so I mentioned that for the first time breeders there’s a substantial minority of males who have a territory but never attract a female at all. And those tend to be the first time breeders who have the smallest dullest bibs.

So in that, in that first year group there’s actually a lot of variation driven by just whether you get a female or not. And a lot of that is determined by bib size. Among the older birds, um almost all of them I think maybe, you know 149 out of 150 older birds that we’ve looked at have a female, have attracted a female.

So there’s not a lot of variation there within-pair. There is some variation in how many eggs the females lay. And there’s, there’s some relationships with that. But it’s not as strong. And there’s not that much variation because they basically, they can lay three, four, or five eggs. And almost all of them lay four eggs. So there’s not a lot of variation in terms of total reproductive success.

There might be something going on, I mean one thing that we don’t really have a good handle on, all the nestlings that we band, so all those 800 nestlings that we band, they leave our site, they migrate south, and we never see them again. So they don’t return to our site they’d return probably nearby our site. Actually we see, I think we’ve saw three again that came back into our site.

So it’s possible that there’s something going on with the quality of the offspring, um where the within-pair mating might be important for determining whether offspring have a high chance of surviving to reproduce as adults. But we don’t have survival data for the nestlings. We just know how many fledged at the end of the season.

[Audience cough]

[Conor] Yeah?

[Audience] Um I was really amazed at your data collection, the methodologies you used to get at all this data, it was amazing, but we were told as kids never to get close to a nest, never to touch a little bird, never to even breathe on it or look at it because it will abandon the nest. Is that all just nonsense?

[Conor] Yeah, I mean for the most part birds, I mean that’s definitely more of a mammal thing than a bird thing because the birds, well this has been challenged a bit, but the classic view is that birds don’t really use olfaction um and so touching the bird is not going to do anything in terms of you know putting your scent on to the bird is where that, typically when people talk about that they think about putting your scent on to the bird.

Now if you’re disturbing the nests, I mean you can cause abandonment. And we’re very careful when we, so I mean we’re out there when we find the nest, but when we’re doing our nest checks we do them as infrequently as possible, and we’ll like, we’ll try. So there actually, people have done experiments on this where if you walk to a nest, and make a path, predators like weasels and things will actually follow the path that you make to find the nest. So we’ll do things like taking you know, big steps over, and leaning over with a stick to look in, and say okay that nest is okay for today. Except for on the day when we have to actually go band. We’ll try to be as minimally invasive as possible.

Okay, thank you.

[Applause]

End of transcript

Learn about three young Cornell researchers’ work. Conor Taff discusses the evolution of the elaborate songs and plumage of male Common Yellowthroats; Sahas Barve from India talks about the coping mechanisms birds use to survive high in the Himalayas; and undergraduate Taylor Heaton Crisologo spotlights strategies used by Herring Gulls to defend their nests and protect their chicks.