The juvenile pliimuj^e of tlic 

 golden eagle is retained for 1 year, 

 the only change being a wearing 

 away of tips of the feathers. From 

 tlie postjuvenile molt on, progres- 

 sive changes take place through 

 annual molts, each bringing the 

 bird a step closer to mature plum- 

 age. At times, one or the other of 

 a nesting ]5air may not have ac- 

 quired its full adult plumage. Tlie 

 fully adult ])lumage is acquired at 

 the age of ']^/2 years, or more ( Jollie 

 1947). 



There is evidence that the golden 

 eagle, contrary to common belief, 

 does not mate for life but that, in 

 the jockeying of birds for better ter- 

 ritories or for more virile mates, 

 new matings are not uncommon 

 (Dixon 1937). 



TERRITORIALITY 



In northern Colorado, the writer 

 observed that each pair of golden 

 eagles occupied a specific territory. 

 Territory referable to the six nests 

 studied there embraced about six 

 townships. Feeding, roosting, and 

 soaring-playing areas w^ere all 

 found within each pair's territory. 

 and the size of these areas varied 

 with availability of food, nest sites, 

 and suitable terrain. 



Dixon, in studying 27 pairs of 

 golden eagles, mapped their tei'ri- 

 tories and kept records ol" their ac- 

 tivities, lie found a dii-ect relation 

 between the amount of actual hunt- 

 ing area axailable to a i)air and 

 the overall size of the territory oc- 

 cupied. As a rule, a ])aii\of eagles 

 in a wihk'rness ai'ea with ample 

 food snp[)lies occtii)ied a smallei- 

 territoi'\' than one whose territor\ 



was planted to crops. Therefore. 

 it can be expected, if other things 

 are equal, that the geographical 

 area occupied by a pair of eagles in 

 hilly country will be smaller than in 

 flat, open country. The minimum 

 area studied encompassed 19 square 

 miles, the maxinmm 59 square miles, 

 and the average for the 27 pairs was 

 about 30 square miles, the equivalent 

 of a townshii). 



Dixon (1937) noted that the 

 bonndaries of the territory claimed 

 by a pair of birds were definite and 

 the area was handeil down from 

 generation to generation. The 

 death of one bird of a pair soon led 

 to the choice of a new mate, and did 

 not affect the status of the area in- 

 volved. If both birds were de- 

 stroj'ed at the same time the area 

 became open territory but did not 

 seem to remain so for long. This 

 was substantiated by the observa- 

 tion that although the female of one 

 pair was kiUed in December, the 

 male had a new mate and a set of 

 eggs was laid In' February 20. 



In describing nesting territories 

 of golden eagles, Baird, Brewer, 

 and Ridgway (1^74) rejxu'ted that 

 in sonthern Oregon each ]iair of 

 eagles seemed to confine itself to a 

 certain district, the nests being 

 about 2<) miles a pa it. AV. Steinbeck 

 of Hollistef. Calif., also observed 

 that each pair had its own I'ange 

 and wonld dri\'e any ontsider away 

 (liendire 1.S92). These fa nges were 

 nsnally from 2 to ('> miles wide, and 

 the hi rds became so att ached to them 

 that it seemed im|)ossil)le to drive 

 them away. In one case, wlu're he 

 took thice sets of eggs in successive 

 M'ais and killed the ft>male, the male 



8 



