- Incubation Period: 34–36 days
- Once incubation begins, the male and female take turns sitting on the eggs, but the female does most of the work. While one sits on the nest, the other is hunting for food or perching nearby to protect the nest.
- Incubation begins after the first egg is laid, meaning that in a nest with more than one egg there will be an oldest sibling, a youngest sibling, and occasionally a middle sibling.
- Both the male and the female have brood patches, though the female has a much more developed brood patch.
- Incubating eagles will sit on the nest almost continuously.
- The eggs need to be maintained at a temperature close to 105 degrees Fahrenheit.
- Adults share incubation duties. Nest exchanges may occur after only an hour but usually take several hours between exchanges. Frequently the incoming adult brings a new branch or fresh vegetation for the nest, then the incubating adult carefully stands and takes off while the other settles over the eggs and rakes nesting material up against its body.
- During nest exchange adults may both be in nest or sometimes one adult may leave eggs unattended for a few minutes before the other adult arrives and resumes incubation.
- The first nest exchange of the day often occurs at or before sunrise, with next exchanges following every 1-4 hours.
- During incubation, an adult will poke around the nest with its bill arranging nest materials and also standing to turn the eggs – it may roll egg(s) carefully with balled feet or its bill, then rock side to side as it settles back over the eggs.
- Incubation posture is flat and low and the bird may not be visible above the level of the nest.
- Adults may vocalize during nest exchanges, to get attention of mate, for example, if a mate is overdue for a nest exchange, or as an alarm call.
- Eggs must be kept warm, shaded from harsh sunlight, and protected from predators.
- In addition to incubating, the eagles also need to turn the eggs about once an hour to ensure that the eggs are evenly heated and that the embryos don't stick to the insides of the shells. When turning the eggs, the eagles often balled up their talons to prevent their sharp claws from puncturing the eggs.
- The eggs are rolled over by either parent about every hour to 2 hours during the incubation period. The purpose of this roll is to make sure that the lighter yolk does not rise to the egg surface and the delicate blood vessels that cover the yolk touch and stick to the shell surface, killing the developing chick.
- The brood patch is an area of bare skin on the bird's breast that is formed when the bird removes its own feathers. By removing the feathers the parent bird allows his/her body heat to better reach the eggs and keep them at the proper temperature.
|
