368 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



the throat ; in a considerable series of young males that I have exam- 

 ined, I have not seen any that did not have at least a few of these violet 

 feathers on the throat; one had a little bunch of them in the elon- 

 gated lateral extension of the gorget only. Later in the season these 

 metallic feathers appear in the crown, but there is not very much 

 progress toward the fully adult plumage until the complete pre- 

 nuptial molt takes place late in winter or early in spring, when young 

 birds become indistinguishable from adults. 



The young female is similar to the adult female, except for the 

 buffy margins on the feathers of the upper parts. Young females 

 can be distinguished from young males by having immaculate, in- 

 stead of spotted, throats. I have seen young females, probably very 

 young birds, that were strongly washed with pinkish buff on the 

 flanks, and more faintly tinged with buff on the throat; the feathers 

 of the head and back in these birds were broadly tipped with grayish 

 buff ; probably the buff soon fades and the tips wear away. 



Both adults and young apparently have a complete molt late in fall 

 and early in winter ; I have detected it in February. 



Food. — The usual hummingbird food nourishes this species; prob- 

 ably it consists mainly of small Diptera, Hymenoptera, and other 

 minute insects, sweetened with nectar or honey from various flowers; 

 the amount of the latter is difficult to determine, as it is not easily 

 detected in the stomach, where it is so soon digested. As to the 

 flowers from which the food is obtained, Bendire (1895) says that 

 "in Inyo County, California, Costa's Hummer seems to be very com- 

 monly found about the flowers of the squaw cabbage, a species of 

 Stanley a., also about wild rose, plum, or cherry bushes {Prmius) 

 growing in the canyons, as well as about other shrubs and plants 

 found in these desert regions." 



Mr. Woods (1927b) says: "During the nesting season it has seemed 

 to me that the female Costa's Hummingbird visits the flowers much 

 less than does the male. At such times the female may often be seen 

 buzzing about inside non -flowering trees and shrubs. While the 

 search may be primarily for cobwebs or other nesting material, nu- 

 merous minute insects and spiders might incidentally be obtained. 

 :i= * * Costa's Hummingbird, for some reason, seems less partial 

 to the Tree Tobacco than do the larger species." 



Dr. Grinnell (1914) says that, in the Colorado Valley, "they were 

 feeding about the spiny bushes of Lycimn andersoni which were at 

 this time profusely laden Avith flowers. A tall-stalked milkweed 

 (Asclepias suhulata) grovv'ing high among the precipitous peaks was 

 also an attraction; so, too, a sage (Hyptis emoryi).'''' 



In probing into the flowers in search of food this and other hum- 

 mingbirds serve a useful purpose for the plants in pollination, as do 



