September

Mating season: Anywhere from late September to early April, depending on the region.
Gestation: The female lays her first egg 5-10 days after mating. The eggs are incubated for about 35 days.
Clutch size: 1-3 eggs.

Immature bald eagles don’t develop their distinctive white head and tail until they are between 4 and 5 years old.

Migration / Dispersal Period
Some eagles migrate. Eagle migration is generally connected to food sources. If an eagle’s breeding territory has ample food sources through the winter, the eagle is less likely to migrate. However, if an eagle’s breeding territory is in northern states where lakes and streams freeze or prey animals hibernate, the eagle will migrate south to find open water and food.  

After leaving the nesting territory both adults and young leave the area. The newly emerging satellite tracking data is suggesting that this dispersal is over a much wider geographical area than we first thought. Most certainly it is generally north to where more food is available early.

Return to Nesting Sites & Territory:
This is happening earlier each year. Generally the adults start to appear about the last week of September through mid October to re-stake claim to their territory. They usually do a little nest rebuilding, maybe some mating and then just hang around to lay claim to the territory.  On the outer west coast, a more wilderness area, we did not see a major return of the breeding adults to their territories until mid to late November.

Caption Page: True Migrants?
Some biologists do not consider or characterize bald eagles as true "migrants", preferring to describe their movements away from and back toward their breeding territories as "seasonal movements". This is because almost all bald eagles only move away from their nesting areas as far as they need to survive, meaning in order to find the food they need to survive. A great many bald eagles (i.e. along the coasts and in more temperate areas like the southeast U.S.) never leave their general breeding areas because they don't need to, and remain there year-round.

Eagles from some areas, however, like the ones we are studying that overwinter in New York State, do have to leave their nesting areas because they totally freeze up in winter and the birds cannot find enough food to survive. Thus, these birds "migrate", but even then depending upon the severity of the winter, they may not follow the same path each year or even go to the same areas each year. For instance in a very mild year, an eagle that moves 1000 miles down to New York to winter from Labrador Province, may only need to move 400 miles to the St. Lawrence River, if they find much open water and food available there. So, keep in mind that bald eagles are not necessarily fixed "migrants" like many other species of birds, that move based upon other cues not related to food availability.

Facts and Photos

• Nesting Timeline