Bald eagles are iconic birds of prey that construct some of the largest nests, often reusing and adding to them year after year. Their breeding season involves a series of intricate behaviors, showcasing a deep commitment to their offspring. This dedication begins well before the eggs hatch, with both parents engaging in significant responsibilities to ensure reproductive success.
Shared Incubation Duties
Both male and female bald eagles actively participate in incubating their eggs, demonstrating shared parental responsibility. While the female typically spends more time on the nest, often taking longer overnight shifts, the male consistently contributes to the incubation process. He provides relief to the female, allowing her to stretch, preen, or hunt, and frequently brings food back to the nest. This cooperative approach ensures the eggs are kept warm and protected.
Both parents possess a brood patch, a patch of bare skin on their belly, which allows for efficient heat transfer to the eggs. Although the female’s brood patch is generally more developed, the male’s participation is crucial for maintaining the necessary temperature for embryo development. When not incubating, the non-sitting eagle often perches nearby, acting as a vigilant guard against potential predators. Nest exchanges between the parents can occur frequently throughout the day, sometimes as often as every one to four hours.
The Incubation Timeline
Bald eagle eggs typically incubate for 34 to 36 days, with an average duration of 35 days. Incubation begins immediately after the first egg is laid, which leads to asynchronous hatching. Eggs in a clutch usually hatch a few days apart, often two to three days between each. Developing embryos require a stable temperature, ideally around 105 degrees Fahrenheit, for proper growth.
To ensure uniform heating and prevent the embryo from adhering to the shell, parent eagles regularly turn the eggs. This process occurs approximately once every hour or two, with eagles using their balled feet or bill to gently roll the eggs within the nest cup. The eggs are rarely left unattended, with incubation occurring almost continuously, sometimes up to 98% of the time. This constant attention is necessary for successful development and hatching.
Beyond Hatching: Continued Parental Care
Upon hatching, bald eagle chicks are altricial, meaning they are born helpless and completely reliant on their parents for warmth, nourishment, and defense. Adult eagles promptly shift from incubation to brooding, continuously keeping the vulnerable hatchlings warm. During the first week post-hatching, the female eagle typically undertakes the majority of brooding duties, spending about 90% of her time directly caring for the young.
The male eagle plays a significant role in providing sustenance during this initial period, often bringing most of the food for both the female and the newly hatched chicks for the first two and a half weeks. Both parents tear food into small, manageable pieces, feeding the young directly beak-to-beak until the eaglets are about five weeks old. As nestlings grow and their appetites increase, both parents share foraging responsibilities more equally.
Eaglets remain in the nest for 10 to 14 weeks before they fledge, or take their first flight. Even after fledging, young eagles continue to rely on their parents for food and guidance. This extended period of parental care typically lasts an additional four to ten weeks, during which adults continue to teach their offspring essential survival skills, including hunting.