Reproduction/Life History

Aquila chrysaetos like some other birds are monogamous by nature and once they have courted will usually stay as a pair for several years. Many birds labeled as monogamous portray a lack of migration and the return to the same nesting sites every year (Watson, 2010). Eagles, similar to all birds, reproduce by oviparity, which means the young come out of an egg after it has been laid. A. chrysaetos concieves in an act called copulation, which is when the male and female touch cloacas to transfer sperm to the female. The courtship and mating processes usually begin to occur around February to mid-April, but breeding season can continue into mid-September (Tesky, 1994). Courtship can be a very beautiful and intricate act, consisting of high soaring, dives, locking talons, and singing (Watson, 2010). Proceeding copulation, around mid-February, is typically when the female will lay her first egg. After the forty-five day gestation period, and continue to lay up to three eggs with around three days in between each lay (Driscoll, 2010).

“Golden eagles (Aquila chrysaetos) nest predominantly on cliffs, but also in trees, and build a number of alternate nests within their territory that they move between in different years” (Driscoll, 2010). These nests are found in the few common locations previously listed and can be quite large. Incubation lasts for thirty-five to forty-five days, during this time the female will do most of the incubating, around eighty-three percent of the time, with the males occasionally trading off at thirteen percent of the time (Watson 2010). After the eggs have hatched the baby eagles, called nestlings at this point, rely heavily on the parents to regulate their body temperature, feed, and protect them (Driscoll, 2010). When hatched the chicks are covered in white down feathers that will be replaced by pre-plumulae down after 15 days (Watson, 2010). Following the down feathers, contour feathers begin to develop starting with primaries, largest flight feathers, then the secondaries, tail and head feathers. At sixty days old the young bird has little to no white down feathers visible. The eagles will take their first flight at around eighty days old (Watson, 2010).

In Watson, 2010 it is stated that for the first few weeks of flight the eagles will stay within one hundred meters of the nesting site. Juvenile eagles will generally migrate about twice as far than older eagles their first time, this can be labelled as the “excursive phase,” which is usually followed by them returning to where they were born. Studies show that non-migratory birds show four stages, “departure from the natal area, exploratory movements, temporary settlements and finally, return to the natal area” (Watson, 2010). Golden Eagles reach sexual maturity at four to five years and start the reproductive process all over again and can live up to twenty years in the wild, reproducing as often as resources and breeding conditions will allow (Driscoll, 2010).

Want to learn more about where Golden Eagles raise their offspring? Visit the habitat page. 

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