260 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



nasal pink. A cuckoo-like kulc JcuJc kuk kuk knk was heard August 12, and a 

 loud unk on July 10 ; the significance of these notes is unknown. 



Mr. Du Bois (1940) writes: "The principal song of the first male 

 was a rather long continuous sentence, usually declarative, ending 

 quite emphatically, but sometimes ending with a rising inflection as 

 though asking a question. The form was somewhat on the order of 

 a warble, but the effect was never very musical. The same bird had 

 an entirely different song, with loud harsh squeaks as a prominent 

 element — a performance difficult to describe, and certainly unique in 

 bird music." 



Mr. Skinner (1925) gives somewhat similar renderings of the song, 

 and mentions a "call, a harsh scolding, though not so harsh as similar 

 calls of the Wliite-eyed Vireo ; uttered as bird moves about tree and 

 bush in search of food. In presence of intruder, a short, exceedingly 

 quick, scolding too-weea-skee or ter-weea-weey 



Pitelka and Koestner (1942) says: "On July 2, Koestner recorded 

 an exchange of place on the nest when, as the male left, the female 

 approached and sang twice. The occurrence of female song in this 

 species was not ascertained further (although suggestive evidence had 

 been recorded on June 22 and 26) ." 



Field marks. — Bell's vireo has no very conspicuous field marks ; it 

 is a plainly colored little bird in merging shades of gray and olive; 

 it has a rather inconspicuous whitish eye ring and one or two whitish 

 wing bars ; and its sides and breast are faintly washed with yellowish. 

 It is mostly to be seen in the haunts of the white-eyed vireo, which has 

 a very conspicuous white iris, or in thickets with the black-capped 

 vireo, which shows a decided black cap. 



It is smaller than the other vireos, and its song is distinctive. 



Enemies. — As it builds its nest so near the ground, its young are 

 easy victims for the cat. Undoubtedly cats and cowbirds are its 

 worst enemies. Mrs. Nice (1931) reports that of 17 nests found in 

 Cleveland County, Okla., 15 were failures, 4 due to cowbirds and at 

 least 3 to cats. Elsewhere (1929) she says that out of nine failures, 

 seven were due to cowbirds; but in no case was a cowbird raised. 

 The first three attempts at nesting studied by Pitelka and Koestner 

 (1942) were failures, probably due to interference by cowbirds. Dr. 

 Friedmann (1929) says that Bell's vireo is a common victim of two 

 races of cowbirds; he has dozens of records in his files. Roy Quillin 

 wrote to him that the vireo "will sometimes build another layer, or, 

 rather, add a layer of lining, and cover up the eggs of the cowbird. 

 They must often push the foreign eggs from the nCvSt, as I have seen 

 many, many eggs of the cowbird on the ground under a nest of this 

 species. Yet the Bell's vireo will hatch the eggs in the majority of 

 cases." 



Other observers evidently do not quite agree with ]Mr. Quillin in his 



