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Nest and Eggs

List of 17 frequently asked questions.

  • Where are the nests located?

    These are wild heron nests located at the Trevor Zoo high above our Australian exhibit for emus and wallabies. Millbrook School’s Trevor Zoo has been a member of the Association of Zoos and Aquariums since 1989, and is the only AZA accredited zoo in the world located at a high school. We may have as many as three or foure active nests all about 85-90 feet up in Norway Spruce trees within the Australian exhibit.
  • Are all the herons wild?

    Yes. The nest is wild and is not enclosed. The herons fish and feed naturally with no assistance from the zoo.
  • Do the herons use the same nest each year?

    The herons have used these nest and others in the spruce trees since 2009. We don’t know whether these herons have been the same individuals 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 a herony in British Columbia found that 13 of 14 individually marked herons chose a different nest site the following year.
  • Where are the other nests?

    The other nests are in trees near the nests that appear on camera. There are five different groups of spruce trees within the zoo that all have nests sites in them. Most years the nests get blow away during winter storms, but are rebuilt each season by the herons.
  • How big is the nest?

    The nest is about 3 to 4 feet wide.
  • 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.
  • When will the eggs be laid?

    This year the eggs were laid between April 8th and Apirl 15th. 2014 the eggs were laid between April 8th and April 16th.
  • How many eggs do Great Blue Herons lay?

    They typically lay 2–6 eggs. This year we had 5 eggs. And in 2014 we had 5 eggs and all hatched.
  • 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. Last year the first egg hatched 28 days after it was laid.
  • No one is 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Can I visit the nest?

    Yes! Millbrook School’s Trevor Zoo is in New York State, about 90 miles north of New York City. It’s open to the public every day from 9 A.M. to 5 P.M. Admission is $6 for adults, $4 for children. Check the Trevor Zoo website at www.millbrook.org/trevorzoo for more information
  • Which parents 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.
  • How big is the territory?

    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. 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!

    The herons located at the Trevor Zoo use a wetland habitat area that covers over 100 acres.


List of 6 frequently asked questions.

  • 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.
  • Do they eat 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.
  • 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.
  • 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.
  • 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.
  • 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 stomach, and 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.

More Heron Facts

List of 4 frequently asked questions.

  • 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.
  • The herons in my area look different than the Trevor Zoo herons. Why?

    Great Blue Herons have a “blue” group and a “white” group. The Trevor Zoo 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.
  • 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 Trevor Zoo 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.
  • 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 have 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.

More About Millbrook School and Trevor Zoo

List of 8 frequently asked questions.

  • Where is the school?

    The main campus sits to the west of the zoo, and can been seen from the cameras. The address of the school is 131 Millbrook School Road, Millbrook, NY 12545.
  • Why can I hear dogs barking?

    Because the nest is located in a zoo, we may hear some strange sounds including howling and barking. The barks and yelps are from the Red Wolves. They are about 100 feet behind the camera, on the ground. They howl every night.
  • What animals are making those sounds?

    The Trevor Zoo is home to White-Naped Cranes, American Rheas, Emus, and Keas. They can often be heard vocalizing in the background. Also, you might hear Trevor Zoo visitors on the ground nearby the nest.
  • Where is the closest pond? Is it manmade?

    There is a pond in the zoo, and about a mile away are some wetlands. The water in the background of the nest is the Trevor Zoo Pond, which is fed by a stream that cuts through the Millbrook School property. As you enter the zoo, you cross a bridge, which has a waterfall on the south side. Below the waterfall is an otter pen. So the river otters have a natural river habitat.
  • 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. The pond is not stocked, however it is stream fed maintaining a supply of White Suckers and Sunnies, and a limited number of large-mouthed Bass.
  • What kinds of wildlife are seen in the zoo?

    The 1,000 acre Millbrook School campus, which is home to the Trevor Zoo, encompasses forests, fields, ponds, and the Seward T. Highley Wetland, is home to all manner of wildlife naturally occurring in the Northeast United States. There are foxes, occasional bears, bobcat, coyote, turtles, waterfowl, and many bird species including Great Blue herons.
  • Is there any invasive vegetation in the area?

    Yes, but usually only in small amounts?

    Purple loosestrife, Garlic mustard and Swallow wort, all of which have ongoing control programs.
  • What kind of vultures are they on the cam?

    The zoo has a population of resident Black Vultures. They visit for a free lunch. They are much more social than Turkey Vultures and are willing to congregate in groups of 30 or more. You will also occasionally see Turkey vultures.

    To learn more about Trevor Zoo, click here.

Parents and Young

List of 21 frequently asked questions.

  • How can you tell which one is male and which one is 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. 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).
  • How old are they when they have their first nest/nestling?

    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.
  • 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.
  • 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.
  • 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.
  • Are you going to name the chicks?

    Cam viewers refer to the chicks based on the order in which they hatch (#1, #2, #3, #4).
  • 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.
  • That baby is 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.
  • 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.
  • When will they fledge?

    Great Blue Heron fledglings leave the nest between 49-81 days.
  • 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!
  • 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!
  • 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.
  • 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.
  • Will the nestlings be okay?

    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. This is called siblicide. In 2014 one chick was killed by the others.
  • 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. This is a live cam broadcasting in real time, so it is 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 Millbrook’s Trevor Zoo we try very hard to help people understand all aspects of nature including the tough moments. We hope that you, like us, will choose to watch, question, and learn from what we see.
  • If a baby dies will the parents eat it? Will they throw it out of the nest?

    In this instance after the youngest chick died both parents attempted to throw it out of the nest with Hudson eventually being successful.
  • When the nestlings fledge where will they go?

    In all previous years all fledglings have headed toward the pond at the zoo located about 100 feet from the base of the nest tree. Whether the fledglings have done this on purpose is not known.
  • If a baby falls out will someone from the zoo 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 and put back (considering dangers to both herons and humans: remember this nest is about 90’ up in the tree); 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.
  • 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.
  • Will the babies come back to the zoo 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.

Anatomy and Senses

List of 8 frequently asked questions.

  • How big are the 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.
  • Do herons sleep?

    Yes. When asleep they will close their eyes.
  • What is the white film that you sometimes see over the bird's eyes?

    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.
  • Do herons have teeth?

  • 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.
  • 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.
  • When it is cold and snowy, are the birds in dange 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.
  • 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!


List of 6 frequently asked questions.

  • When was the camera installed?

    These current cameras were installed in the trees on March 24, 2017.

    Our first year of streaming the heron nests was 2014, and we have done it every year since.
  • How did you get the camera in the tree?

    The cam weighs 7 pounds and is installed 90 feet up a neighboring spruce tree. It is attached to a 20-foot 40-pound camera mount. The mount is constructed from 2” PVC pipe housing conduit inside for the cables used to power the cam and transmit the picture. The mount secures the cam to the tree and helps stabilize the picture and provides support to the tree so that the weight of the camera does not snap the top of the tree.

    Mike Hearn of Mike Hearn Tree and Landscape, helped install the cameras this year with his climbing expertise. He got both cameras up in the trees in a matter of hours.

    The microphone is positioned on the mount about 15 feet away from the nest. No climbers disturbed the birds.
  • Do the cameras bother the herons?

    No, the herons usually ignore the camera. Occasionally they peer at it, perhaps because they see their reflection.
  • How long will the cameras stay on?

    The cam will stream during the entire nesting season.
  • What type of camera do you use?

    The camera on the South Nest is an Axis P5636-E Mk II pan-tilt-zom camera(https://www.axis.com/us/en/products/axis-p5635-e/)

    On the Infirmary Nest we have an Axis P5414-E pan-tilt-zoom camera (http://www.axis.com/products/cam_p5414e/)
  • Who set up the camera?

    In 2014, Millbrook School senior John Norfleet '14, decided to focus his CES (Culminating Experience for Seniors) project on setting up a bird camera on campus. His hard work resulted in our heron cameras! It was a learning experience for the whole team that allowed us to streamline the process year after year.