DNA Tests Determine Whether 2013’s Injured Hawks Came From Bird Cams Nest

By Pat Leonard
August 29, 2014
Red-tailed Hawks Photo of Big Red and Ezra from Cornell Lab Bird Cams.

It was just over a year ago, on the same day, that two young Red-tailed Hawks were injured in separate accidents on the Cornell campus. One was found dead; the other was euthanized because of the severity of its injuries. Many people feared the young birds were the offspring of Big Red and Ezra, the beloved hawk pair that have nested on campus for years and have been featured on our live Bird Cams since 2012. But there was no way to tell for sure.

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It was the not-knowing that bothered Cornell University employees Christine and Steve Bogdanowicz. But unlike most Bird Cams fans, they were in a position to investigate. Steve is an evolutionary biologist who turned his expertise with DNA analyses to determine the hawks’ familial relationships. He directs the Evolutionary Genetics Core Facility at Cornell University. Christine is the Assistant Director for Academic Programs for the Shoals Marine Lab and a Birder on the Ground. These “BOGs” are a dedicated group of local, volunteer hawk enthusiasts, most of whom work on campus. They follow the birds in their spare time and report to the wider Bird Cams community.

So, were the two dead birds the offspring of Big Red and Ezra? It took hard work (all by volunteers), plus feathers, tissue samples, and another injured hawk to clear up the uncertainty. And when the answers emerged they were surprising: one yes and one no.

DNA testing confirmed that the fledgling found injured in 2013 was the offspring of Big Red and Ezra and a female. She was most likely D1, the eldest of the 2013 brood. Photo by Christine Bogdanowicz.

Steve learned that the bird found severely injured does appear to be one of the young hawks from Big Red’s and Ezra’s 2013 “D” brood. This bird, a female, was known as “D1” to the hawk cam community. The other young bird, the one that had been found dead, had been assumed to be “D3.” This bird, a male, turned out not to be related to Big Red or Ezra and must have come from another hawk nest in the area.

In October 2013 Steve began the necessary DNA work using tissue samples from the two dead juvenile hawks sent over from Cornell’s Animal Health and Diagnostic Center. His goal was to create a library of specific genetic “markers” for Red-tailed Hawks—something that did not exist at the time. During the fall of 2013, Steve developed 15 microsatellite DNA (msat) loci (locations) from the samples.

“Msats are simple, relatively short, repetitive sequences interspersed throughout otherwise complex genomes,” Steve explains. “Humans, Red-tailed Hawks, plants, and other animals typically have tens of thousands of distinct msat loci.” Finding a set of specific markers that can be used as a basis for comparison is the same technique used to identify human crime suspects or establish paternity.

To establish relatedness, Steve also needed to get DNA from Big Red and Ezra and one of their known offspring for comparison. That didn’t happen until 2014. Another dedicated BOG and Cornell staffer, Karel Sedlacek, collected feathers he witnessed drop from Big Red and Ezra and passed them to Steve. (Note: Sedlacek was issued a special permit to take these feathers. It is otherwise illegal to do so.)

Young Red-tailed Hawk "D3," offspring of Big Red and EzraE3, a fledgling from Big Red and Ezra’s 2014 nest, was also injured and is recovering at the Janet L. Swanson Wildlife Health Center. E3’s DNA sample was a crucial part of determining the identities of the 2013 hawks. Photo by Dr. Noha Abou-Madi.

Then E3, a bird hatched by Big Red and Ezra this year, was injured after fledging. The Janet L. Swanson Wildlife Health Center is caring for him and was able to provide a blood sample.

“E3 was key,” says Christine. “His sample solidified what an offspring of Big Red and Ezra would look like genetically.”

“DNA extracted from an individual hawk can be amplified through a process called polymerase chain reaction (PCR) at each of these microsatellite loci,” says Steve. Amplification means the PCR process increases the amount of DNA available, creating enough genetic material to visualize and measure. A separate test to determine gender was made possible by Laura Stenzler at the Cornell Lab’s Fuller Evolutionary Biology lab.

Sample results from 1 of the 15 microsatellite loci used in the DNA analysis. Like humans, birds receive one copy of their DNA from each of their parents. By lining up the peaks in the graphs, it’s clear that E3 received one copy of this locus from Big Red and another from Ezra. By comparison, the mystery hawk has two copies of the same allele (and thus shows only one peak). That peak does not match either Big Red or Ezra, indicating he is not related to either of them, and therefore cannot be D3. Photos: Big Red and Ezra by Christine Bogdanowicz, E3 from the Janet L. Swanson Wildlife Health Center.
Young Red-tailed Hawk "D3," offspring of Big Red and EzraDNA testing established that the fledgling found dead in 2013 was not related to Big Red or Ezra. D3 (above) may still be out in the wild somewhere. Photo by Christine Bogdanowicz.

Steve’s work established that E3 had DNA markers showing he inherited one PCR fragment (allele) from Big Red and another from Ezra at each microsatellite locus—just as humans inherit one copy of each parent’s DNA. Any offspring of Big Red and Ezra would inherit one PCR fragment from each parent for all 15 of the loci—all 15 loci have to match, as they did for E3. (The figure below shows 1 of the 15 loci.) If there is even one mismatch, that’s enough to rule out that bird as being related. And that’s what happened with the mystery juvenile originally thought to be D3.

There are many other Red-tailed Hawks in and around the Cornell campus. Some hang out near the horse paddock, others live along nearby cliffs, and still others frequent a nearby cemetery. Perhaps the mystery juvenile came from one of those groups. Steve has gotten tissue bank information for about 40 red-tails that the Wildlife Health Center has taken in since 2011. With that and any future samples gathered, he could start building up a profile of what the local Red-tailed Hawk population looks like and determine relationships from a tangle of overlapping territories.

“Now we’ll be able to focus on these 15 established markers to determine if birds come from an isolated population or if there’s gene flow between two or more populations,” says Steve. “We can learn family-level relationships and individual identity. Big Red and Ezra have produced maybe 20–25 offspring over the last decade. Are any of them back in the area as adults? I’m doing this work because I’m curious, primarily, and because of the mystery of the two dead birds last year.”

“Maybe it’s a little bit of closure,” says Christine. “There was so much hurt and angst, anxiety and sorrow. But these birds will not have died in vain if we learn from them. They’re helping us understand the family of Red-tailed Hawks that live in this area and maybe beyond.”

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  • This is such a welcomed article on our hawks and look forward to knowing if and how many of Big Red and Ezra’s young ones might be in your area.

    Thank you for taking on this much needed project.

  • Kate

    Your dedication and expertise amaze me. Thank you so much for sharing it with all of us back yard birders.

  • Sarah Judson

    I’ve heard that Redtails can actually kill or injure their own young sometimes. Is this true?

  • May I use this space to say that many of the people who watch these camera’s and follow all of the wonderful people at Cornell and volunteers give so very much to all of us in the work and time they dedicate to these wonderful creatures called birds that we share this ear with. We thank you. What a difference you have made in my life.

  • Claudia Aguirre

    This is fascinating and wonderful work. Thank you Steve and Christine.

  • Mike Ballard

    Thank you so much Mr. and Mrs. Bogdanowicz, for all your efforts in this follow up, as well as your BOG and documentation efforts. Bless you! This takes a bit of the sting from the unfortunate events of 2013. In early 2012 I stumbled upon Cornell’s Hawk Cam in a Google search for something else. Big Red and Ezra already had three eggs in the nest, and from that moment I was hooked. We continue to spread the word about your bird cams. Once again, thank you, and best regards to all.

  • Wallissa Dippold

    What a fascinating report. I remember the news when the two young hawks were found. It was truly heartbreaking. I almost decided not to watch again this year, but the lure of watching nature at its best couldn’t be stopped. I have learned so much and continue to do so with reports such as this and the truly inspirational work done by so many there and around the globe. Please continue to share this valuable information with us. Thank you so much. Wallissa

  • Jennifer Sergeant

    This is HUGE and exciting information! Thank you Steve, Christine, Karel and Cindy for your constant dedication!! I cannot wait to see the whole area’s family dynamic. It does make me wonder where D3 was after the accident. Thank you Cornell!!

  • Sarah Hamilton

    So very interesting. It does give me a bit of closure. All of us watchers felt the loss of these beauties. Thank you to all involved.

  • This was so informative and interesting. Thank you for developing this method of identifying the young birds and comparing them to Big Red and Ezra. Such good work you all do there; I am proud to belong to your organization. Keep up the great work. Thanks for your hard work.

  • Cindy LaBare

    I found this article very interesting. It also made me happy to hear that our beautiful D3 may still be out there somewhere. Thank you for your dedication!

  • John Blakeman

    No,this virtually never, ever happens. Any reports of such are highly questionable. I’ve done field studies of wild Red-tails across the continent, done state and federally authorized Red-tail rehabilitation, field banded dozens of wild Red-tails, (and much more with this species) — and have never encountered (nor read an authenticated case) of adult predation on offspring or other immatures.

    Yes, haggards (resident adults) will chase vagrant immatures out of established territories, but no injury or killing is involved.

    –John Blakeman

  • Rose Slosser

    They do not band the young from this nest then? Strictly just a nest cam to observe? I see at least one parent is banded.

  • Dianne Lawson

    This is so exciting and a wonderful service Christine & Steve have provided for the Cornell hawks. Thank you so much for your dedication & hard work.

  • We are very honored and proud to be part of this project — you are all most welcome! Big Red, Ezra and all of their offspring have brought us joy and teach us the wonders of Mother Nature in so many ways. Thank you all for caring and for following our special hawk family.

  • Natalie

    So glad this report. I am so happy that D3 is quite possibly alive and well somewhere in the surrounding area.
    Thanks to all who made this possible. Your hard work gives us closure. We now know D1 had to be put down, but that the other bird, was not D3 as previously presumed. Thank God for this!

  • loveschocolate

    Thank you to Christine, Steve and all of the dedicated BOGs who continue to educate us! Nature is full of surprises! It’s heartening to know that D3 may still be out there adding to the gene pool! Miss everyone! Coffee anyone -[___]?

  • Rose, Big Red and Ezra are both banded; if you go to the Cornell Lab of Ornithology hawk cam page you can find out about when and where they were banded. Big Red is banded on the right leg, and Ezra is banded on the left leg. None of the Big Red and Ezra offspring have been banded. Here is the link to the hawk cam page–enjoy! http://cams.allaboutbirds.org/channel/16/Red-tailed_Hawks/

  • Holly Farish-Hunt

    Amazing research that reveals SO much about our beloved BR and Ezra family! Thank you ever so much for your curiosity, dedication and contributions to both the veterinary professional community as well as we “watcher followers” of both Cornell RTHs and Ospreys. These ongoing experiences of watching, sharing and reading have enriched my life beyond words. I’m already thinking about 2015 and continue looking up.

  • captivated64

    Thanks Chris & Steve. Does single spike in graph for Mystery Hawk indicate/suggest its parents were related?

  • Amy Jarratt

    Thank you so much for posting this information. Very,very interesting material.Please keep us up to date with any new information.Thanks

  • Sarah Judson

    Thanks. I had mentioned to someone at a local raptor program that I’d seen a bunch of redtail feathers beneath an established nest. The feathers were just emerging from their sheath, so I thought they might be from a young one. She said sometimes they attack their own young…I’m glad it’s not true ;-)

  • John Blakeman

    This is exactly why there is the “no-kill zone” and its related behavioral suppressions in hawks and eagles. In the vacinity of the active nest, the hawks’ innate predator desire to kill and consume downy and vulnerable prey is suppressed. Away from the nest, beyond the no-kill zone, any downy or vulnerable bird will be attacked and killed, as an easy meal.

    In the case of the observed sheath-emerging feathers beneath a nest, those could only have come from some other predator, most likely a Great Horned Owl (a species noted for plucking the feathers of avian prey).

    (And that would have involved some aberrant behaviors on the part of the resident adult Red-tails; as they seldom allow owls anywhere near a nest, a factor the owls perceive and seldom challenge. Great Horned Owl predation at Red-tail nests is very uncommon, for a long list of reasons too detailed to elaborate on here. In this case, the resident adults may have been killed away from the nest by accident [vehicle collisions, or other factors] leaving the unfledged eyass weak and vulnerable.)

  • Sarah Judson

    We *do* have Great Horned Owls on the property…

  • Barbara DeHamer

    Fascinating information! I look forward to learning new things about the red-tailed hawks. Thanks to all involved.

  • John Blakeman

    And obviously, the owls did not slay the eyass Red-tails when they were most vulnerable, in the downy stage.

    It doesn’t work out well for Great Horned Owls that slay Red-tails, either eyasses or adults. Owls are unable to construct nests; they usually expropriate a constructed nest from a Red-tail, usually in December, before Red-tails begin nesting. Afetr losing their last-year nest to a pair of owls, the Red-tails just move a half-mile or so elsewhere, and build a new nest — which is very seldom preyed upon by the adjacent owls.

    Great Horned Owls that slay Red-tails simply kill the providers of their nests. Consequently, hawk-killing genes in Great Horned Owls are not highly selected-for.

  • Rose Slosser

    Thanks Christine, I am fairly new to this page, I’ll be sure to check things out. I have a soft spot for birds of prey.

  • Leslie Mensak

    E3’s injury was indeed a tragedy yet through your work and diligence it led to the identification of D1, his older sister, and gave us all hope that D3 is still out there. Thank you so much.

  • Jamila Hammad

    If D3 survived that stormy night, can anyone explain a possible reason why D3 was never seen again near his parents? I remember afterwards BR and Ezra teaching D2 how to hunt, etc. It seems very strange to me that D3 would have simply gone away exactly after that night. I’m not questioning the findings of the DNA study, I’m just trying to better understand what could have happened. Thank you!

  • h tucker

    Thank you Steve, Christine, Karel & Cindy. This is an amazing effort, and closure we wished for but had not expected. How fortunate we are for the Cornell Lab of O and its bird cams, the passion, enthusiasm, talents, dedication and generosity with which you and all the BOGs take us beyond-the-nest — and now to benefit from Steve’s joining the cause with his expertise and interest…the mind boggles at the doors through which his involvement and efforts may lead us all!

  • Leslie Hoffman

    Thank you so much for your work and this article! It’s wonderful to know that E3 is already making his contributions to deeper knowledge about his wonderful family. I just started watching this year and was totally and completely hooked. It’s been almost a month since the last update on E3. I’d love to hear how he is doing and what the prognosis is for whether he will eventually be able to be released into the wild.

  • Peggy Hart

    Very glad I checked in. This is very interesting and informative. I started watching the allaboutbirds.org in 2012. The RTH are beautiful birds and love watching them. Thank all of yu or your hard work and educating us.

  • birdlady9

    The article refers to D3 as a male and D1 as a female. Is this an error, or was the hawk community mistaken on the sex of the two juvenile hawks?

  • Cheryl Fox

    It’s silly, but I had tears in my eyes when I read that the dead juvenile wasn’t D3. People all over the world were willing D3 to finally fledge, and we all had a spot in our heart for him. It’s wonderful to know he is probably flying about as a healthy big boy(or girl!)

  • Chickaddict

    Thank you sooooo much for this scientific information! I have watched BR/EZ hawklet cam for the past three years from afar and have learned so much from all the people involved. Please keep posting any new information and any updates about the injured hawk! Thank you, thank you!

  • birdlady9

    This article states that the hawk found injured, D1, was a female. Is this an error, or was the hawk community incorrect in identifying D1 as a male?

  • Dear birdlady9:
    The DNA tests found D1 to be a female, yes; this is not an error. The hawk community (myself included) all did think that bird was a male based upon size. While male raptors are very often smaller than females, the best way to determine the gender of a bird is by using DNA analysis. Unless of course you see the bird laying eggs as we do with Big Red every year ;-)

  • Dear Jamila:
    In August/September of 2013, we were seeing juvenile Red-tailed Hawks on and near campus after that storm–we assumed that we were observing D2 only, but it’s possible we were seeing D2 and D3. It’s very, very difficult to identify individual RTHs even though we try hard to keep track of “who’s who”–they all look alike! The best way to keep track of fledglings from a single brood would be to have them color banded–but at this point, there’s no plan to do so. We’ll have to just keep enjoying them and watching in wonder as they share their daily lives with us on and near campus ;-)

  • birdlady9

    Thanks so much for this information, Christine, and for all you do! Just goes to show, the birds continue to teach us something new all the time. ;)

  • You are most welcome birdlady9!!

  • Dear Leslie Hoffman,
    You are most welcome–weI surely know what you mean about being “hooked” ;-) If you check the RTH page–there is an update about E3; here is the link: http://cams.allaboutbirds.org/channel/16/Red-tailed_Hawks/
    Thanks for joining in on this journey…

  • Dear captivated64:
    Your question is a very good one! The “spike” you refer in the Mystery Hawk’s graph simply means the bird inherited the same allele from each parent at that micro sat locus. So no, this doesn’t mean it’s parents were related? I hope this helps. You can contact me at ccb5@cornell.edu if you would like to get some more information ;-)

  • RRassendyll

    Stupid article. Lauds some wonky biologist, ignores the problems that Cornell poses. This and related stories aim at spinning Cornell as a good place for birds. What utter twaddle. Cornell is part of the ancien régime, the problem, and no tweaking will fix it. Tear the place down, and sow the soil with salt.

DNA Tests Determine Whether 2013’s Injured Hawks Came From Bird Cams Nest