Hanover Bald Eagle Blog # 15 -2022
April 18, 2022
In partnership with Pennsylvania Game Commission and Comcast Business .
It’s been 27 days since first hatch and 26 days since second hatch. The Hanover nestlings are almost one month old! Weeks four to seven are considered the “middle third” of the nestling period.
Bald eagle nestlings put on roughly 4 ounces of weight per day when they are between 18 and 24 days of age, which, for the Hanover kids, was last week. That was the highest rate of weight gain they will experience during their time in the nest. Now, at 26 and 27 days old, their skeletal, muscular, and neurological growth is ramping up. They will require a constant influx of nutritious food to fuel their transition from helpless nestlings into curious eaglets. This is part of why bald eagle parents start breeding when they do — they time their nesting schedule so that plenty of food (primarily fish) is available during this period of intense growth.
This stage of bald eagle family life is many people’s favorite to watch, and for good reason. The little ones are becoming mobile, exploring their surroundings, and their appearance is objectively comical. Their feet and beaks, for example, are disproportionately large, giving them a clown-ish look.The youngsters rely on these appendages to adjust their position, receive food from their parents, and preen their developing feathers. During sibling conflict, which we are seeing little of, a nestling may also use their beak to attack or defend themselves. Adding to the youngster’s amusing pre-teen look is the fact that their feathers are still sprouting along tracks of their body, giving them a disheveled bed-head appearance. They also fall on top of each other often, which is both adorable and normal — coordination takes time, and the young eagles won’t master control of their limbs until they are a little older.
As the nestlings grow, their behavior will change, as will the behavior of the parents. Right now the parents are still very attentive, but they are starting to leave the nest for short periods of time. Once the nestlings are fully feathered, the parents will focus more of their energy on hunting and will spend less time inside the nest, while continuing to stand watch nearby.
The growth rate of raptor chicks depends on several factors including the species, the sex, and how much food is available. Falcons, for example, develop much more quickly than bald eagles. They are smaller and have different life histories. Peregrine falcons fledge between 35 and 42 days old, while bald eagles don’t fledge until they are between 55 and 100 days old. The potential fledging window is much larger for bald eagles, and their growth rate is slower.
Male bald eagles grow more quickly than females, although these differences are nearly impossible to verify in the nest from observation alone.
Before we know it, the nestlings will begin exploring the edges of the nest, toying with sticks, and testing each other’s interpersonal limits.
Fun Fact
The youngsters consume roughly four fish per day!
Sources
Bildstein, Keith L. (2017). Raptors: The Curious Nature of Diurnal Birds of Prey. Cornell University Press.
Bortolotti, Gary R. (1984). Physical Development of Nestling Bald Eagles with Emphasis On The Timing of Growth Events. Wilson Bulletin, 96(4), 524-542. usask.ca/biology/bortolotti/pubs/wb96-4-524-542.pdf
Gerrard, Jon M. & Bortolotti, R. Gary. (1988). The Bald Eagle: Haunts and Habits of a Wilderness Monarch. Smithsonian Institution.
The Center for Conservation Biology. (2020). Facts About Bald Eagles. https://ccbbirds.org/what-we-do/research/species-of-concern/virginia-eagles/facts-about-eagles/#:~:text=Q%3A%20Why%20do%20eagles%20eat,get%20caught%20in%20their%20crops.
Newton, Ian. (1979). Population Ecology of Raptors. T & A D Poyser Ltd.
Raptor Ecology Specialist - Zoey Greenberg
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