450 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



alike and closely resemble the adult female. The adult female is like 

 the adult male, but she has no black on the head, no green on the 

 throat, and the postocular stripe is buffy instead of white. Mr. 

 Eidgway (1911) says that the young male has the "throat spotted 

 with metallic emerald green or yellowish green." And the young 

 female, he says, is "similar to the young male but without green on 

 the throat." 



Mr. Brewster (1902), who had a large series of these birds, taken 

 every month in the year except October and January, makes the 

 following general remarks on the seasonal variations in plumages : 



The summer and autumn birds ai'e by far the brightost colored, having the 

 green of the back quite pure ; the black of the forehead, sides of head and chin, 

 deep velvety often glossed vpith violet or blue ; the metallic green of the throat, 

 clear and brilliant ; the cinnamon rufous of the under parts, rich and pure. 

 The spring birds (March, April, and May) are uniformly much duller and 

 paler, the green of the back being much tinged with ashy or rusty, and the 

 black of the head with brown, while the green of the throat is muddy in tone 

 and but slightly iridescent. 



One bird (No. 17,031, Triunfo. April 11, 1887) has the black of the head 

 confined to the auriculars, and the green of the throat to a few central spots, 

 the rest of the under parts being dull cinnamon rufous, and the entire upper 

 parts dull green with most of the feathers tipped with rusty cinnamon. 



This specimen is evidently a young mnle that is beginning to as- 

 sume the adult plumage at its annual complete molt. Judged from 

 what is available in the literature and what can be learned from the 

 study of specimens, it seems that the young of both sexes are, at first, 

 like the adult female with no green on the throat ; and that the young 

 male soon begins to acquire some metallic green feathers on the 

 throat, but does not assume the fully adult plumage until the next 

 spring; I have seen young males acquiring the green throat in April 

 and in July, and in full molt in July. I have seen adults molting in 

 July. 



Food. — Not much is definitely known about the food of Xantus's 

 hummingbird, which probably does not differ essentially from that of 

 other hummingbirds, with due allowance for the species of insects 

 and feeding plants to be found in its habitat. Dr. Frederic A. Lucas 

 (1893) lists: '■^Cecidomym., Phora., three specimens of Solenopsis 

 geminatus., elytra of beetle, Psylhi.s, parts of spiders." 



Behavior. — Mr. Lamb (1925) has this to say about the habits of 

 this hummer: 



At one place the hummingbirds' bath was discovered, where a trickle of water 

 flowed over a flat rock a short distance and then dropped in a tiny waterfall. 

 At one time I counted nine birds at once taking a bath. They would sit in the 

 water and give themselves a thorough shower with their wings; then, to finish 

 off, they would fly against the falls, breast first, and then they would back up 



