376 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



The disagreement in the figures of Bowles and Dickey as to the 

 age at which the eyes are opened is probably due to the fact that 

 the eyes are habitually kept closed for a good while after they are 

 capable of being opened. Despite the great number of nests described 

 or recorded, there seem to be few published figures on the length of 

 time the young Anna's hummingbird remains in the nest. The single 

 occupant of the nest watched by Mr. Anthony left after 18 days, 

 undoubtedly a shorter than average time, since the period of three 

 weeks recorded by Mr. Bowles corresponds very closely with my 

 determinations for Costa's and the black-chinned, which range from 

 20 to 23 days for each species. This period in the case of the hum- 

 mingbirds is more uniform than it is with most species of passerine 

 birds and averages at least 50 percent longer. 



Plumages. — The molting of the body plumage, as indicated by a 

 slightly unkempt appearance, seems to take place in July and August. 

 The luminous feathers of the crown and gorget are not replaced at that 

 time, however, but begin to be shed in October, the ruff being com- 

 pletely lost and the throat and head becoming decidedly ragged, the 

 former showing streaks of gray. The entire process to the completion 

 of the new gorget requires perhaps a month. During this time the re- 

 mainder of the plumage shows no sign of molting. The practice of 

 the "nuptial flight," in so far as I have observed, seems to be discon- 

 tinued during this period. 



The outline of the gorget becomes visible on the throat of the 

 young male soon after it has left the nest. The area gradually be- 

 comes sooty black, with glints of red, and slowly grows redder, the 

 throat feathers lengthening into a ruff. Even in fall, however, when 

 this first gorget is apparently complete, it still is lacking something 

 in brilliancy and form; but it is almost immediately shed, to be 

 replaced by the full perfection of the adult. 



In the male Anna's and Costa's hummingbirds, alone among the 

 species occurring in the United States, the crown is like the throat 

 in color, but the two differ from each other not only in the color 

 of the gorget but in its shape. As viewed from the front, that of 

 Anna's is deeper and its lower border forms nearly a straight line, 

 while the lower outline of the Costa's gorget is decidedly concave and 

 its ruff is narrower and more prolonged. In both, the area of the 

 crown is separated from that of the throat by a light streak running 

 backward and downward from the eye, but in the Anna's only a very 

 narrow gray line divides the luminous area behind the eye from that 

 of the crown. 



Among hummingbirds, and especially in the present species, indi- 

 vidual variations seem more pronounced than among most birds. 

 The color of the back ranges from slightly bluish metallic green to 

 decidedly bronzy green in different individuals; the rose-red of the 



