With 10,000 species of birds on earth, there’s a lot of variety in their methods for nesting, incubating eggs, and raising young. You can see this on the Hays bald eaglecam and the Cathedral of Learning peregrine falconcam, now that there are eggs in both nests. Here’s what we’ve seen already.
Bald eagles …
- Place their nests in trees within sight of water.
- Build their nests of sticks and line them with grasses
- Begin incubation(*) immediately, as soon as the first egg is laid.
Peregrine falcons …
- Place their nests on sheer cliffs (traditional nest site) or on buildings or bridges that resemble cliffs.
- Don’t “build” a nest. Instead they use a high ledge that has deep gravel, dirt or dust and scrape a bowl in the substrate to hold the eggs.
- Delay incubation until the next-to-last egg is laid. Note that when it’s cold and there are only one or two eggs in the nest, the adult bird will periodically cover the eggs without heating them.
The photo above shows Hope perched at her nest before dawn without “sitting” on her first egg. Even though the temperature was close to freezing at the time, she didn’t have to keep the egg warm because she hadn’t begun incubation.
And here’s Terzo guarding the egg while Hope eats breakfast.
If you’re used to nesting robins, chickens and bald eagles, peregrines are certainly different.
(*) Incubation is when the bird opens its belly feathers and lays its bare skin against the eggs to heat them. Constant warmth is required for the embryo to develop.
(photos from the National Aviary snapshot falconcam at Univ of Pittsburgh)