454 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



a thicket, only 2 or 3 feet above ground, sometimes higlx, exposed 

 ones, such as the dead twig of a pine tree 40 feet in the air. One 

 bird, which engaged much of my attention, regularly alternated be- 

 tween a perch less than a yard from the ground in a thicket of 

 raijon bushes, and an exposed dead twig in the top of an alder tree 

 growing beside the thicket, fully a dozen times as high. Sometimes 

 a strong wind caused a wliite-ear whose favorite perch was lofty and 

 exposed to descend to some lower, more protected position close at 

 hand. Whatever the nature of the station he had chosen, the bird 

 was to be found there day after day, week after week, throughout 

 the months of October, November, and December. When I departed 

 the region at the end of the year, a number still sounded their little 

 calls from the very spots where I first encountered them early in 

 September. 



Perhaps the most typical note of the male white-eared humming- 

 bird in the singing assembly is a low, clear tink tink tink^ sounding 

 like the chiming of a small, sweet-toned silver bell. At least this is 

 the note that I first discovered, and the one that I like best to remem- 

 ber. Some individuals toll their little bells very rapidly, others more 

 slowly and deliberately. But as I began to know more and more 

 white-ears, scattered over miles of mountainside, I came to realize 

 that there was a surprising degree of variation in their voices. Many 

 individuals persistently sounded notes so different from the usual 

 clear tinkle that I did not recognize them as the utterances of white- 

 ears until I had laboriously stalked the birds and actually watched 

 them as they called. These notes were dull and flat, with no trace 

 of the clear timbre characteristic of the majority of the species, or 

 else high and squeaky, or low and melancholy. One that I frequently 

 visited uttered rapidly and monotonously a single clicking note, a 

 kind of harsh metallic buzzing almost painful to hear. 



These individual differences in voice were surprising enough in 

 themselves, but even more remarkable was the fact that the same 

 type of voice was likely to be common to all the members of a singing 

 assembly. If one bird of a group uttered a clear, silvery tinkle, his 

 neighbors would be found to sing in the same strain; if I happened 

 to be attracted to an assembly by a chirping note, I usually found 

 that this note was common to all the members of the group. There 

 were, of course, exceptions to this rule, but these were not sufficiently 

 numerous to make me doubt its validity. But what is the explana- 

 tion of this phenomenon? Not impossibly it was the result of imi- 

 tation, and all the members of an assembly merely copied the vocal 

 peculiarities of one bird that happened to be the first to begin to 

 sing, or in some manner dominated his neighbors by his personality. 

 But I suspect that the real cause was deeper. The individual varia- 



