Nest and Eggs
1. Where is this nest located?
It’s in the Cornell Lab of Ornithology’s Sapsucker Woods Sanctuary. The nest is 50 feet high in a dead white oak tree in the Sapsucker Woods Pond. The nest is about 46 inches from the trunk of the tree to the outer rim.
2. Do the herons use the same nest each year?
Great Blue Herons have used this nest above Sapsucker Woods Pond since 2009. We know that the same male has nested here since at least 2009 (we can recognize him because he has a missing toe). We don’t know whether the female has been the same from year to year. Great Blue Herons don’t always return to the same nest or choose the same mate from one year to the next. One study at another location found that 13 of 14 individually marked herons chose a different nest site the following year.
3. Do they mate for life?
Not necessarily. Great Blue Herons are usually monogamous during any one season, but they may choose a different mate the next year.
4. When will the eggs be laid?
In 2012, the female at this nest laid her eggs on March 28, March 30, April 1, April 3, and April 6. Great Blue Herons usually lay an egg every two or three days until the clutch is complete.
5. How many eggs do Great Blue Herons lay?
They typically lay 2–6 eggs. In 2012, the Great Blue Herons at Sapsucker Woods Pond laid five eggs. Great Blue Herons at higher latitudes and in freshwater habitats tend to have more eggs per clutch on average. The herons in Sapsucker Woods successfully raised four young each year in 2009, 2010, and 2011, and five in 2012.
6. How long does it take for the eggs to hatch?
According to the scientific literature, Great Blue Herons usually incubate their eggs for about 26-29 days. In 2012, the eggs in the Sapsucker Woods Pond nest hatched 30-35 days after the first egg was laid. The first two eggs hatched on April 27. The others hatched on April 28, April 30, and May 2. Once begun, the process of hatching out of the egg can take up to 48 hours.
7. No one’s sitting on the eggs. Won’t they get cold?
It’s normal for the parents to leave the eggs exposed now and then. In most cases, they don’t stay away long enough for the eggs to suffer harm.
8. How warm do the eggs have to be? Why do the parents roll them?
Eggs develop at about 37-38 degrees Centigrade, about 98-100 degrees Fahrenheit. The parents roll the eggs to warm them evenly, and so the embryos will not “stick” to the inside of the shell.
9. What happens if the eggs are damaged?
If only one egg is damaged, the parents may continue to incubate the other ones. If something happens to the entire first clutch of eggs, herons usually try again at another nest.
10. Why hasn’t one of the eggs hatched even though the others have hatched?
Great Blue Herons typically lay an egg once every two or three days until their clutch is complete. They start incubating as soon as the first egg is laid. The eggs that are laid first have a head-start and hatch sooner than the ones that are laid last. In some cases, however, an egg may not hatch because it wasn’t fertilized or because the embryo didn’t develop properly.
11. What is “pipping”?
"Pipping" refers to the process of initially breaking through the shell with a hard projection on the bill called the egg tooth. The resulting hole is the "pip" which the chick then enlarges to finish hatching.
12. When the chick is still in the egg how does it get air to breathe?
Heron chicks may take up to 48 hours to make their way out of the egg. Oxygen gets into the egg through pores in the shell. The chicks get their first big gulp of air when they pierce the membrane of the egg under the shell a day or so before pipping. Once they pip, they keep their bill close to the pip and the growing crack they're working on.
13. Which parent sits on the nest?
Mom and Dad switch off anywhere between 20 minutes and 22.5 hours. They hunt and eat when they are off the nest. Usually the female incubates at night.
14. Can I visit the nest?
Yes! You can see the heron nest from the trails along Sapsucker Woods Pond and from the observatory in the Cornell Lab of Ornithology’s visitor center. Please visit us. Directions are available on our website.
15. How big is their territory?
The Great Blue Herons here have been observed hunting all across the 10-acre Sapsucker Woods Pond. In 2009, one nesting pair chased away another pair that attempted to nest in another tree above the pond. However, there is a lot of variability in heron territory size and in the territorial behavior of Great Blue Herons, probably related to the abundance and distribution of food as well as nesting sites. A study of 32 territories in Yaquina Estuary, Oregon, found that the mean territory size was 21 acres, but in freshwater marshes the mean size was only 1.5 acres. Great Blue Herons are not always territorial and may hunt for food within several yards of one another, but at times will defend an area by displaying, threatening, and chasing other Great Blue Herons. Unlike the herons in Sapsucker Woods, Great Blue Herons typically nest in colonies, usually with fewer than 500 nests per colony, but at least one colony of more than 1,000 pairs has been recorded!
Parents and Young
16. How can you tell which one is the male and which one is the female?
Male and female Great Blue Herons look alike. Adult females are generally smaller than adult males and the ornamental plumage in males has been found to be longer on average, but these differences can be hard to discern. Because you can get a close-up view through the cams, you may be able to notice differences between individual birds. For example, in 2012, viewers could recognize the male because he had a missing rear toe. The female appeared to have a rufous (reddish) patch on her left shoulder, and partway through the breeding season she lost the plume on her head. She will regrow the plume, but it enabled viewers to recognize her easily at the time. Some researchers believe that the length of the exposed culmen (upper ridge of a bird's bill) can accurately sex herons (about 5.5” in males; 4.8” in females). The only way to tell for sure is by DNA testing or by observing behaviors (for example, witnessing the female lay an egg, or observing the male perching on the back of the female during mating).
17. How old are they when they have their first nest/nestlings?
Great Blue Herons usually start breeding during their third spring (at about 22 months old), though some have been observed attempting to breed during their first year.
18. Are the young herons boys or girls? How can you tell them apart?
We can’t tell which young herons are male or female just by looking. In general, the biggest nestling is the first one that hatched and smallest is the last one that hatched.
19. Won’t the babies get smothered from parents sitting on them?
The parents don’t sit down on the chicks hard enough to smother them. The chicks can breathe even when their parents are brooding them.
20. How old are the herons when they leave the nest?
Great Blue Herons usually fledge when they are about seven or eight weeks old. In 2012, the herons at Sapsucker Woods Pond fledged 60-69 days after the first nestling hatched. The first three herons fledged on June 26. The last two departed the nest on July 3 and July 5. The exact dates of fledging will vary from year to year.
21. When do they get adult plumage?
By the time Great Blue Herons are two years old they will have most of their adult plumage, though it may not be 100% complete until their fourth spring.
22. Are you going to name the chicks?
In 2012, cam viewers referred to the chicks based on the order in which they hatched (#1, #2, #3, #4, and “Fiver”). We’ll probably continue this tradition.
23. Are you going to band the chicks?
Banding birds with an individually numbered ring on their leg is a common practice in ornithology to mark and study individual birds. Special permits are required to band birds for scientific study. If the herons were needed in a study, then we would consider banding them, but presently the birds are not part of a study and we do not plan to band them. In order to avoid unnecessary disturbance at the nest, banding nestlings is done only when scientifically warranted.
24. That baby’s crying. It sounds hungry! Why haven’t the parents fed it?
Keep watching. You’ll probably see the parent come in with food before long. As the young grow, the parents may stay away from the nest for longer periods of time. In cases of severe food shortages, it’s possible that some young may starve. However, Sapsucker Woods Pond seems to have plenty to offer. In 2012, the herons successfully fed and fledged all five of their young.
25. How long until the babies can see?
Eyes open when the young hatch, but it is unknown what their vision is like upon hatching and how long it may take to develop.
26. When will they fledge?
Great Blue Heron fledglings leave the nest between 49-81 days. In 2012, the young fledged 60-69 days after the first nestling hatched. The exact dates of fledgling vary from year to year.
27. How big are the nestlings?
A newly hatched chick weighs about 50 g (1 ¾ ounces). At 1-2 weeks they are about 6 inches; 2-4 weeks almost 12 inches; 4 to 6 weeks almost 4 feet!
28. Won’t the babies fall out of the nest?
It is very rare that a nestling will fall out of a nest except in extreme circumstances, such as a predator attack. Nestlings seem to know that they shouldn’t stray far!
29. Why is that big one picking on that little one?
This is a natural, well documented behavior for nestlings of some bird species, including Great Blue Herons. Sibling rivalry often develops among young herons, so it’s normal to see this. The older siblings are usually bigger and have an advantage when jabbing at the younger siblings. During food shortages, the older chicks may be the only ones to survive. Fortunately, Sapsucker Woods Pond seems to offer plentiful food. In 2012, viewers often worried about the smallest chick, but all five young received enough to eat and successfully fledged.
30. What causes sibling aggression?
In some cases, the aggression may be a way for the birds to tussle and hone their skills, such as when kittens or puppies in a litter tumble about and fight. Aggression can also result from competition for food. Studies indicate that the young herons are more likely to compete aggressively if the food items are small and are delivered to them directly, beak to beak, from the parents. The hypothesis is that when small prey are delivered in this way, there is an advantage for the young to jockey with one another for the best position. In 2012, the Sapsucker Woods herons typically delivered larger food items (whole fish) by depositing prey on the floor of the nest rather than directly into the young's beaks and though there was some rivalry for food, all of the young herons survived and thrived.
31. Will the nestlings be OK?
Sometimes behaviors that look alarming, such as repeated jabbing, do not result in serious injury. In other cases, especially during food shortages, intense aggression may result in one sibling killing the other. Because prey is abundant in the area, we hope that all the young will survive.
32. Why don’t you shut the camera off during displays of sibling aggression?
We understand that people often feel upset when they witness events in nature such as predation, fighting, injury, or death. If we observe serious injury and distress, we will redirect our web page to an interim page that provides information about what is happening and that enables people to choose whether or not they wish to continue watching.
However, because this is a live cam broadcasting in real time, it possible that viewers will see upsetting events. Viewers must decide for themselves whether they are comfortable enough with this possibility. If not, they may wish to stop visiting the cam page.
The heron cam is an opportunity to see an intimate, 24/7 view of nature as it is. The lives of these birds have touched and inspired hundreds of thousands of people. As in real life, however, nature shows us beautiful and profound moments, as well as moments that seem tragic or difficult to comprehend at times. At the Cornell Lab of Ornithology, we look to nature as our teacher. We hope that you, like us, will choose to watch, question, and learn from what we see.
33. If a baby dies, will the parents eat it? Will they throw it out of the nest?
We’re not sure, since this circumstance has rarely been observed. We hope all the chicks will survive, but if not, we will all learn the answer by watching the cameras together.
34. If a baby falls out will someone from Cornell put it back?
It would depend on the circumstances. We would need to consider factors such as whether the young heron can be safely captured; whether it is old enough to survive on its own with its parents looking after it; whether it is injured and can be rehabilitated; and if so, what its quality of life would be.
35. Do the parents look after the nestlings after they leave the nest?
After the herons fledge, they may come back to the nest for about three weeks.
36. Will the babies come back to Sapsucker Woods Pond next year?
We don’t know, since we won’t be able to recognize them. Very little is known about where the young herons go during the winter and where they return in spring. Studies of individually marked herons show that the young disperse in all directions two to three months after the breeding season ends. One juvenile Great Blue Heron that was banded in the United States was later found in Belize! A study of more than 3,000 juveniles showed that they disperse an average of 471 miles during their first winter.
37. What do Great Blue Herons eat?
Mostly fish, but also amphibians, invertebrates, reptiles, mammals, and birds. There has even been a report of a heron scavenging (eating carrion). It appears that prey species and foraging habitats may change over the life of a heron as it perfects its hunting techniques.
38. Do they eat the bones too? Why do they eat the bones?
Herons swallow their prey whole. They eat the bones because there is no way for them to fillet their fish! Also, the calcium and other nutrients in whole prey items are great nutrition for the birds. Herons are able to digest almost all of the prey that they swallow, but will cast out indigestible pellets. They have very acidic stomach secretions that protect their stomachs from being punctured by sharp bones: Herons swallow the fish whole, so the bones aren't exposed at first, and by the time the bone ends are exposed, they've been softened by acids.
39. How far do they travel to find food?
If the nest is not located right near a feeding area, herons may travel 1.5-4 miles to their main feeding areas. Some individuals go as far as 18 miles, but most stay within a 2-mile range.
40. How often do they eat?
Herons forage throughout the day. When raising hungry chicks, they spend almost all of their time hunting to find enough food.
41. How do they get water?
They get water mostly through their diet as fish and other dietary items contain sufficient fluids to keep the birds hydrated.
42. That bird just threw up. Is it sick?
Herons will sometimes “cast” (regurgitate) indigestible parts of prey, such as hair, in the form of a pellet. Parents carry fish and other prey in their throat pouches, then regurgitate the meal into the nest for their young to eat. Young herons may vomit over the side of the nest when alarmed; this discourages predators.
Anatomy and Senses
43. How big are herons?
Great Blue Herons usually weigh 4.6-5.5 pounds. They can be up to 4.5 feet tall and have a wingspan of 5 ½ to 6 ½ feet.
44. Do herons sleep?
Yes. When asleep they will close their eyes.
45. What’s the white film that you sometimes see over the bird’s eye?
Birds have what is known as a nictitating membrane or “third eyelid.” This is a clear eyelid, closest to the eyeball. It is transparent and can close and protect the eye when hunting.
46. Do herons have teeth?
47. Why is the poop white?
Bird poop is actually brown; the white pasty excrement is uric acid, the equivalent to a mammal’s urine. Mammals excrete waste as urea dissolved in urine. Birds excrete it as uric acid which has a low solubility in water, so it comes out as a white paste.
48. Do herons have a sense of smell?
We’ve always assumed that most birds have a poor sense of smell because the area of a bird brain involved in smell is relatively small compared to the area found in mammals. However, recent research reveals that birds have a high number of active genes that are associated with smell. Scientists have also discovered that some species of birds can tell each other apart by smell. So, though we don’t have all the details, herons probably do have some ability to smell.
49. When it’s cold and snowy, are the birds in danger of freezing to death?
Great Blue Herons can tolerate very cold winter temperatures. Under normal circumstances, it is unlikely that a healthy heron will freeze to death. It’s important for them to keep their feathers in good condition for insulation, and to be able to find enough food to maintain their body temperature.
50. Why is it standing on one leg?
Though this may happen due to injury, there are other reasons why birds sometimes stand on one leg. They may do this as a heat-saving measure, keeping the raised leg warm against their stomachs, or as a way to reduce fatigue in the raised leg. Birds may also stand on one leg to look more camouflaged when hunting prey as two legs may look suspicious to ground level or aquatic prey. Birds may also shift legs just to be more comfortable, in the same way a human will re-adjust their position!
More Heron facts
51. What predators are threats to Great Blue Herons?
Bald Eagles and Great Horned Owls are known to kill adult Great Blue Herons, and there is at least one report of a juvenile being killed by a Harris’s Hawk. Bald Eagles, Common Ravens, and American Crows will eat unattended eggs. Bald Eagles, Common Ravens, raccoons, bears, Turkey Vultures, Red-tailed Hawks, and nonnative fire ants are known to eat nestlings. In 2012, a Great Horned Owl attacked the Sapsucker Woods heron nest at night several times, but the female heron successfully defended the nest.
52. The herons in my area look different than the Cornell herons. Why?
Great Blue Herons have a “blue” group and a “white” group. The Cornell herons are part of the “blue” group. The white group is found in coastal areas of southern Florida and in the West Indies. These groups can interbreed and produce young that can have a variable appearance. You may also observe other similar-looking species in your area, such as Tricolored Heron or Great Egret. See photos of different heron and egret species.
53. Will the herons migrate? Where will they go?
Most Great Blue Herons migrate to some extent, even if just a general movement away from the northern edge of their summer ranges. They usually go southward, but always head to where there is open water. Migration usually occurs mid-September to late October. Usually they return to their breeding grounds by February or March. It’s unknown where the Sapsucker Woods Pond herons go and whether they stay together. Herons may migrate on their own, but they have also been seen in groups of up to 100 during migration. The young also migrate but it is unknown if young stay with parents during migration. Parents usually stop interacting with their young in August or September, right around the time when the young leave the area.
54. How long do herons live?
The oldest known Great Blue Heron was 23 years old. However, the average age in the wild is probably much younger. Based on data from studies of birds that has individually numbered bands on their legs, mortality is estimated to be 69% in the first year, 36% in the second year, and 22% in subsequent years. Based on calculations, the average age of a breeding adult Great Blue Heron in British Columbia is estimated to be 5.6 years.
55. Do the cameras bother the herons?
No, the herons usually ignore the camera. Occasionally they peer at it, perhaps because they see their reflection.
56. How long will the cameras stay on?
The cam will stream during the entire nesting season, as well as the rest of the year if we have the funding to keep the cam streaming.
More on Sapsucker Woods
57. How deep is the pond? Is it manmade?
The pond at Sapsucker Woods is a manmade structure that averages one meter deep, but can be up to two meters in a few areas. Sapsucker Woods sits at the top of a hill and has soil with very poor drainage. About a meter to two meters below the surface is a nearly impermeable layer called a "fragipan.” This impermeability keeps the soil too wet to be reliably used for agriculture, and is the reason why Sapsucker Woods was never clear-cut for farming.
58. Is it a pond or a bog? Does water move through the pond? If runoff from rainfall stops, will the water level in the pond decrease?
Water in the Sapsucker Woods area moves from the southeast to the northwest; a large wooded swamp in the eastern part of the woods has a very slight bowl shape that captures rainfall and directs it to the northwest, where the pond is located. Water travels underneath the Sapsucker Woods Road through large culverts and eventually flows through to the main pond. Take a look at an aerial photo of the area by clicking here. On the northwest side of the main pond there is a flood control structure, basically a height -stabilized outlet, and this outlet is where the small watercourse snakes off to the NW. Because the water flows though the pond in this way, the pond is not a bog. Water from the pond eventually connects with the rainwater control/sewer system and makes its way down to Cayuga Lake. Because there are no springs leading to the pond, water levels will fall if rainfall is low. However, if beavers are living in the pond, which they do sometimes, the water level can also stay high.
59. What kind of fish are in the pond?
No one has ever determined all the species of fish in the pond, and the list may change from year to year. Because the pond has connected watercourses, it's hard to say what kinds of fish are in there at any given time and how they got there. There are no records, but in the past there may have been some stocking of fish in the pond, and also a fair bit of dumping. It's also possible that fish make their way to the pond on their own from connected downstream sources such as culverts. Watching what the herons bring for their nestlings, we do know that the pond has catfish, pumpkinseed sunfish, and carp (including goldfish).
60. What kinds of wildlife are seen in the Sapsucker Woods?
The 230-acre Sapsucker Woods sanctuary encompasses forests, ponds, and ferny swamps, and is home to lots of wildlife. Click here for a list of birds found in the area. There are abundant reptiles and amphibians; frogs provide a non-stop chorus during the spring and summer months. Mammal species include squirrels, chipmunks, opossums, rabbits, skunks, raccoons, deer, foxes, coyotes, beavers, muskrats and bats to name a few.
61. Is there any invasive vegetation in the area?
Yes, but usually only in small amounts. In the Sapsucker Woods there is garlic mustard, crown vetch, yellow iris, and eurasian milfoil. There has been a fair amount of purple loosestrife that has been knocked back through the use of nonnative bio-controls. There is also a lot of invasive black alder that was erroneously planted instead of speckled alder many years ago.
To learn more about Sapsucker Woods, click here.