Bald Eagle age

A Bald Eagle becomes sexually mature at the age of four to five years. Prior to that it undergoes substantial changes in appearance which enables its age to be estimated. All the variations can be seen around the Lake, as local eagles do not migrate.

Adult Bald Eagles mate for life. In February, they show serious breeding behaviour: they add new sticks to their existing nests and mate. By the end of March, eggs have been laid. Chicks hatch late in April. By mid-July, the young have fledged.

Descriptions are given of the Bald Eagle in the winter when its appearance is not in the transition which takes place during the protracted molt (feather replacement) of spring and summer. This table relies heavily, but not exclusively, on McCollough, Mark, 1989, “Molting sequence and aging of Bald Eagles”. Consult it for more detail, and good drawings.

Appearance of a Bald Eagle by Age
Age	Head	Body	Image
Chick  in nest	plumage: grey down ⇒ brown feathers beak, cere: blackish iris: sepia	plumage: grey down ⇒ brown feathers	unavailable
Juvenile  fledged  ½ yr	plumage: blackish brown crown: slight bleaching by winter beak, cere: uniformly dark grey iris: sepia	underparts: buff brown mottled dark wing coverts: dark brown wing pits: mottled white tail: sooty black mottled white
Basic I  1½ yr	plumage: brown crown: tan beak, cere: mainly dark grey iris: lightens to buff–brown	tail: brown body, wings: dark brown wing pits: mainly white mantle: mottled white triangle breast: mainly olive belly: darker than breast
Basic II  2½ yr	plumage: the osprey–head look crown: light grey auriculars: brown band to eye throat: extensive white beak: blackish grey, buff–yellow cere iris: light cream	tail: smokey grey going to mottled brown at tips body, wings: brown occasionally mottled white wing pits: variable, mottled white
Basic III  3½ yr	plumage: striking shift to white crown: brown flecking, also around and behind eye beak, cere: mainly yellow, brown line forward of nares iris: pale yellow	tail: white, terminal brown strip body, wings: dark brown with scalloped buff feather margins; slight white flecking on chest and wing pits	unavailable
Basic IV  4½ yr	plumage: same as III except almost no brown mottling on head	tail: white body, wings: same as III	unavailable
Adult  5½ yr ⇒	plumage: white beak: yellow iris: pale yellow	tail: white body, wings: dark brown with scalloped buff feather margins