Journey North Bald Eagles: Spring Phenology

Bald Eagle

Spring Phenology of Eagles
Watch for these events to occur on the nesting grounds.

Date	Behavior
	Arrival on Nesting Territory: Migratory individuals only. Males and females of mated pair seem to appear on territory within a short time of each other.
	Defending Territory: Watch for skirmishes with other eagles and, during nesting, with other birds. Intraspecific aggression less noticeable when pair has been established for many years.
	Courtship: Displays involve aerial acrobatics and tumbling, but are rarely seen.
	Nest Building: Nests made of sticks lined with softer grasses and mosses. The same nest is often used for many years. Both male and female build.
	Mating: Eagles are monogamous, meaning males and females have only one mate. Pairs stay together for life. If one dies, the remaining bird finds a new mate and usually carries on in the same nesting territory.
	Egg Laying: First laid several weeks after arriving at nest site. Typicially, two eggs laid, the 2nd egg 1-2 days after first. If a 3rd egg, it's often laid a full week after 1st egg.
	Incubation: Lasts 34-36 days, begins as soon as 1st egg is layed, "asynchronous incubation." Males and females take turns, but female does bulk of work.
	Hatching: 1st egg hatches before 2nd egg, the same number days earlier as it was laid. Young are semi-altricial when just hatched: immobile, downy, eyes open, fed by parents.
	Nestling Stage: Lasts 10-12 weeks, both parents share feeding responsibilities. Older eaglets more likely to survive due to size/age differences due to competition for available food.
	Fledging Stage: In years with plentiful food, very commmon for 2 or even 3 to fledge. This stage lasts 4-6 weeks, both parents continue to feed, but young also forage on own.