346 REPORT OF NATIONAL MUSEUM, 1890. 



more golden or brassy hue, particularly on the tips of the feathers, this 

 condition characterizing all of the three Mexican (winter?) specimens in 

 the collection, besides several of those from the United States. The 

 color of the top of the head varies from an almost coppery bronze to a 

 decided green hue. 



Adult females vary chiefly in respect to the throat, which may be 

 entirely without any metallic feathers, but usually has a more or less 

 extensive irregular patch of metallic golden red ; but there is also much 

 variation in the extent and intensity of the light cinnamon-rufous of the 

 sides and flanks. 



Young males may be immediately distinguished from females by the 

 much greater amount of rufous on the tail, the four middle feathers 

 being chiefly of that color, though the terminal dusky spaces are much 

 more extensive than in adult males, the white tips and subterminal 

 black spaces of the other rectrices being essentially as in the females. 



Although the mature plumage of the male usually first begins to 

 make its appearance on the throat, there is a specimen in the National 

 Museum collection (No. 79915, Marin County, California, April, 1880) 

 which although having assumed entirely the adult plumage so far as 

 other parts are concerned has only a single metallic feather on the 

 throat. 



Of all our western Humming Birds, the Rufous-backed has the widest 

 distribution, its breeding range extending from the mountains of Ari- 

 zona to latitude 61 on the coast of Alaska, and from the Pacific coast 

 to New Mexico and Colorado. It must not be inferred from this gen- 

 eral statement, however, that the species breeds everywhere within the 

 wide extent of territory thus defined, for, on the contrary, certain con- 

 ditions of climate and vegetation, dependent on altitude as well as lati- 

 tude, are necessary for its existence. In Colorado, for example, it is 

 said to breed only above an elevation of 6,500 feet, ranging thence up 

 to 10,500 feet,* although in the Santa Catalina Mountains of southern 

 Arizona, so much farther south, its breeding range is said to be between 

 4,000 and 6,000 feet elevation,! 



In Ventura County, California, it is said to be the most abundant 

 species of the family during summer;| but Mr. Beldiug says that in 

 the Sierra Nevada it is a rare summer resident above 4,000 feet. It 

 seems not to occur at all in Lower California, except possibly as a cas- 

 ual visitant or straggler, since Mr. Belding never met with it during 

 his several explorations of that peninsula. 



For original observations on the habits of the Kufous Humming 

 Bird, we owe more to Mr. H. W. Henshaw than to any other writer. 

 Mr. Henshaw found it " by far the most abundant of the family in New 

 Mexico and Arizona, as shown in every locality visited by our party. 



* Drew, Auk., in, 1885, p. 17. 

 t Scott, Auk, in, 1886, p. 431. 

 tEvermami, Auk., HI, 1886, p. 180. 



