during the summer of 1941, the 

 senior author recorded 677 bald 

 eagles along 837 miles of shoreline. 

 Other eagles, particularly the less- 

 conspicuous immature birds, no 

 doubt M'ere present but were not 

 seen. After making allowance for 

 them, it was believed that an esti- 

 mate of 12 to 15 eagles for each 10 



miles of shoreline was a reasonable 

 one. Concentrations were observed 

 usually in areas of alnindant food, 

 as on Baranof Island, where for a 

 distance of 6 miles along the shore 

 and up a salmon stream, at least 45 

 eagles were seen. At one point 

 along the stream 19 birds were in 

 sight at one time (fig. 2). 



CHARACTERISTICS 



PLUMAGE 



The newly hatched bald eagle is 

 clothed in a thick, light-gray down 

 whicli fades into white on the head 

 and underparts (fig. 3). In about 

 3 weeks, this first down is followed 

 by another coat of darker-hued 

 down that is retained until it is 

 pushed out by the young bird's Ju- 

 venal plumage. The juvenal plum- 

 age begins to appear when the eaglet 

 is 5 or 6 weeks old, and is rather 

 uniformly brown with flight 

 feathers of the wings nearly black. 

 It is the plumage of the young 

 birds when they leave the nest at 

 about 12 weeks of age and is re- 

 tained until the first annual molt, 

 which takes j^lace during their 

 second summer (figs. 4 and 5). 

 Through subsequent annual molts 

 the bird ultimately acquires the 

 whiteness of head and tail so char- 

 acteristic of the species. Complete 

 maturity of plumage is not attained 

 until the bird is 3 or more years old 

 (frontispiece). Etta S. Wilson 

 (1922) described a captive bald 

 eagle which retained its juvenal 

 plumage through its third year, but 

 the feathers of both head and tail 

 were pure white a year later. On 



the other hand, Lee S. Crandall 

 (1941) has reported the develop- 

 ment of the plumage of a captive 

 bird which did not acquire a white 

 head and nearly white tail until its 

 sixth year and did not possess a 

 completely white tail until its 

 eleventh year. Once attained, the 

 immaculate whiteness of the head 

 and tail are retained throughout 

 the rest of the bird's life. 



AGE 



Little is known of the length of 

 life of bald eagles living in the 

 wild, but the longevity of captive 

 birds may be construed as an indi- 

 cation of what happens when the 

 hazards of outdoor life are re- 

 moved. Stott (1948), summarizing 

 longevity records of birds in the 

 San Diego, Calif., zoo, reports two 

 eagles that lived 15 years. 



SEX RATIO 



That the sex ratio of the bald 

 eagle is about 1 : 1 was revealed by 

 the dissection of 187 specimens by 

 the senior author in the course of 

 his Alaskan fieldwork in 1941. Of 

 these, 54 were immature birds, half 

 of which were males and half 



