286 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



bridize ; and there is some evidence to support this theory. William 

 Brewster (1906) reported that, during two seasons, a bkie-headed 

 vireo repeatedly sang both songs in his garden ; and he suggested the 

 possibility that it might have been paired with a yellow-throated vireo, 

 though he had no evidence to prove it. Dr. Charles W. Townsend 

 (1920) says : "On May 8, 1919, a bird that sang the wild clear song of 

 the blue-headed vireo so that there seemed to be no mistake about its 

 identity turned out to be be a yellow-throated vireo." And Bagg and 

 Eliot (1937) have this to say on the subject. 



Throughout the fifteen years 1921-35, according to Prof. Eliot, the Smith Col- 

 lege Yellow-breast has sung the same song. * * * iq 1930 (but not again) 

 another male took up quarters in the same neighborhood who sang two songs — 

 his own species' and the Blue-headed Vireo's. Inspection showed that he looked 

 darker, especially about the head, than normal for his kind; and suspicion was 

 at least aroused that in the scarcity of Yellow-throated females his father (pre- 

 sumably the Smith College male), perhaps widowed, had persuaded a Blue-head 

 to mate with him, the year before. * * * lu Agawam on May 26, 1936, the 

 song of a blue-head, seeming very out of place, was looked up and found to 

 issue from a typical-looking Yellow-breast (Eliot). Apparently the fiavifrons 

 coloration is "dominant" in hybrids. Probably it was that of the two species' 

 common ancestor, and soUiarius originated as a northern variant or "sport". 

 * * * On June 22, 1936, near Mt. Tekoa (not at all Yellow-breast country), 

 Mr. Dietrich studied a Blue-head with a yellow wash on the throat and "incom- 

 plete eye-ring" — possibly the effect of Yellow-breast blood? 



This is an interesting theory, but it is strange that no hybrids have 

 found their way into collections ! 



Field marks. — The yellow-throated vireo should be unmistakable, 

 with its brilliant yellow throat and breast, only slightly less brilliant 

 in the female than in the male, its olive-green back and its double, white 

 wing bars. No other northern vireo is so brightly colored. It is much 

 more deliberate in its movements than any of the warblers, less slender 

 in form, and has a heavier bill. It looks something like a pine warbler, 

 but this warbler frequents the pines, whereas this vireo is almost always 

 seen in deciduous trees. Its color pattern is somewhat like that of 

 the yelloW'-breasted chat, which is seldom seen away from dense 

 thickets, is larger, and has a much longer tail ; the behavior of these 

 two is very different. The contralto voice of the yellowthroat will 

 also distinguish it from other vireos. 



Enemies. — Probably the principal reason for the almost complete 

 disappearance of this and other vireos from our New England urban 

 and suburban districts has been the wholesale spraying of our shade 

 trees. Ludlow Griscom (1923) wrote of the New York City region: 

 "Our handsomest Vireo was formerly a common summer resident 

 throughout the area from early May to the middle of September. 

 While many of us had noted a slow but steady decrease in numbers in 

 the last 20 years, no one was prepared for the sudden and rapid dis- 

 appearance of this species since 1917 over the whole suburban section, 



