386 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



Gerald H. Thayer wrote to Dr. Chapman (1907) : 



In a grouping based on songs, the Bay-breast should stand in a quintette with 

 the Blackburnian, the Black-poll the Black and White and the Cape May. 

 These five heard singing together in the same trees, as I have heard them on 

 the Hudson River, make 'confusion worse than death' for any bird-student but 

 the most adept. But with patience and a good ear one can learn to differentiate 

 them surely. All five are thin-voiced, "sibilant," singers ; but each has its own 

 slight, prevailing peculiarity of tone, in addition to the differences, varied 

 but never wholly violated, of phrasing and accentuation. The Bay-breast's 

 singing, in the spring at least, is the most liquid and inarticulate of the lot, and 

 sometimes the loudest. It varies greatly, from the bases of at least two and 

 probably three clearly distinct main songs. In one of these, the six or more 

 barely-separated lisping notes are all alike in volume, accentuation, tone, and 

 speed. They are slightly louder than the Black-poll notes, and not quite so 

 smooth in tone. Another song begins in about the same way, but ends with 

 three or four clearly-separated louder notes, which have a more nearly full- 

 voiced ring. A third, uncommon, song, which I have all but surely traced 

 to the Bay-breast, is louder throughout, and otherwise very different. It begins 

 with about ten penetrating notes, in close-knit couplets like those of the Black 

 and White's shorter song, and of much the same tone, but louder ; and it ends, 

 abruptly, with a single, lower-toned, much richer note, like a fragment of Oven- 

 bird song. 



Philipp and Bowdish (1917) say : "The song is of a character quite 

 similar to that of the Blackburnian Warbler, but slightly stronger 

 and louder. It is delivered for long periods, with considerable fre- 

 quency, and at all times of day, though less frequently toward the 

 middle of the day. It appears that the female sings from the nest, 

 in answer to the male, and the song is markedly weaker, being scarcely 

 distinguishable from that of the Blackburnian Warbler. The ap- 

 proach of an intruder is apt to cause the female to become silent." 



Field marks. — The adults of both sexes are unmistakable, with their 

 conspicuous chestnut markings on crown, breast, and sides, black 

 cheeks and a buffy spot on the side of the neck, in spring plumage, the 

 females being duller in colors and with less chestnut. Fall birds 

 might easily be mistaken for blackpolls, which they closely resemble, 

 but adults usually have some trace of chestnut wash on the sides, less 

 streaking above, and none below. Young birds have no trace of chest- 

 nut on the sides. The under tail coverts of the bay breasted warbler 

 are cream-color, while those of the blackpoll are pure white. 



Fall. — Bay-breasted warblers are often very common on the fall 

 migration, sometimes really abundant. That they are sometimes com- 

 moner than we realize is a result of the difficulty of distinguishing them 

 from the blackpolls as the two are migrating through the treetops 

 together. As a rule, however, the bay-breasted warblers are earlier 

 migrants, passing through New England during the last half of 

 August and the first week of September, then in company with the 

 blackpolls for the next two weeks, after which very few of them may 



