April 17 notes: two eaglets in our nest!

This morning after a prey delivery (a duck?) we watched the parent eagle feeding two chicks. She meticulously reduced the prey to small morsels and carefully fed both chicks. One chick is older and larger than its sibling and is the first to be fed. The smaller chick will continue to do well as long as plenty of food is available. Sibling competition for food and mortality from starvation or infanticide is greatest in the first two weeks when the size difference between the two chicks is the greatest.

For most of the time, the chicks will remain out of view of the web camera. They cannot maintain their body temperature when they are young and downy. Notice how the parents sit differently on the nest in a more upright posture. On rainy days, the wings of the adult act like an umbrella to keep the chicks dry.

The chicks will remain downy for the next two weeks. At that time, we should start to see some black pin feathers, which will replace the down. If chicks are fed well, they grow about 100 grams per day. Maximum growth occurs when they are about 3 to 4 weeks of age.

For the first two to three weeks after hatching, the female is present at the nest about 90% of the time and the male about 50% of the time (out of view of the camera). You will often hear one of the adults calling to its mate or tilting its head upward to watch its mate soaring overhead. Once the chicks start to grow feathers and can maintain their body temperature, the parents will begin perching off the nest.

Bald eagles are extremely sensitive to disturbance at this critical time. To flush an adult eagle from the nest exposes the chicks to cold, wet weather or predators. When we review development projects, we always request that activity near the nest during the incubation and early chick-rearing period be avoided. -- Mark McCollough, U. S. Fish and Wildlife Service