THE HUMMING BIRDS. 349 



The very close resemblance in coloration between this species and 

 8. rufus is really remarkable, the only obvious differences in the male 

 consisting in the green instead of rufous back and the smaller blackish 

 terminal markings of the tail-feathers ; but the different shape of the 

 tail-feathers is so decided a character that even were the coloration 

 absolutely identical in the two they could nevertheless be easily distin- 

 guished. The females are still more alike in color, the only difference 

 that I am able to find, with only two females of 8. alleni for comparison, 

 consisting in the markings of the tail-feathers, the middle pair of which, 

 in 8. alleni, have much more rufous, while a considerable portion of 

 their tips is black, this black being either more restricted or even 

 wholly absent on the same feathers in 8. rufus. The under tail-coverts 

 are also deeper cinnamon-rufous; with a large series for comparison, 

 however, these apparent differences may be found to disappear, so that 

 it would be necessary to depend entirely upon the really very great dif- 

 ference in the width of the exterior rectrices in order to distinguish 

 females of the two species. 



Allen's Humming Bird so closely resembles the Rufous-backed in 

 general appearance that unless specimens are actually obtained it is 

 not easily identified; consequently its range is not well made out. 

 That its range is far more restricted than that of the common species 

 is, however, quite certain. It is essentially confined to the coast dis- 

 trict of California, but reaches into British Columbia on the north. 

 Only one specimen has been recorded from auy locality outside of Cal- 

 ifornia to the southward, the one in question having been taken in the 

 Santa Catalina Mountains, Arizona, at an altitude of 4,500 feet, July 

 23, 1884, by Mr. W. E. D. Scott.* According to Mr. Belding, it has 

 not yet been found in central California; arrives at San Diego, from 

 the southward, at about the same time as S. rufus; is quite a rare sum- 

 mer resident at Santa Cruz, and is not common in San Bernardino 

 County. It appears to be more numerous in Nicasio County than else- 

 where, and it was there that Mr. C. A. Allen, of Nicasio, obtained the 

 fine series of specimens that enabled Mr. Henshaw to define the char- 

 acters of the species. Mr. Henshaw was furnished by Mr. Allen with 

 observations on its habits, which are well worth reproducing here. 



Mr. Allen remarks incidentally in a letter that the green-backs, as he 

 calls individuals of 8. alleni, are much the livelier and more active of the 

 two, keeping constantly in the open and always perching on the most 

 prominent dead twigs they can find. Their extreme shyness, as con- 

 trasted with the unsuspicious nature of the rufous-backs, is quite re- 

 markable. They seem to possess a larger share than usual of the cour- 

 age and pugnacity which is constantly displayed in birds of this family. 

 Not only do they always come off the victors when chance encounters 

 take place between them and the rufous-backs, but Mr. Allen has seen 

 a pair attack and put to rout a Red- tailed Hawk; while, as he remarks, 



* The Auk, vol. in, 1886, p. 431. 



