YELLOW-THROATED VIREO 285 



of proclaiming itself at a season when most of the migrants — and a 

 large proportion of the resident birds, too — are songless." 



Mr. Ford mentions in his notes "a disturbed trill, which may be 

 likened to the wing sound of a flushed mourning dove, albeit much 

 diminished. This seems to be used only when the bird is in attend- 

 ance upon the young. Its scolding note is unlike the whining com- 

 plaint of the warbling vireo and the red-eye. It is a sort of chatter, 

 in tone similar to that of the agitated house wren." These are, ap- 

 parently, the same notes as those described above by Mr. Saunders. 



Francis H. Allen writes to me : "A call note that I have heard in 

 May and which may be connected with courtship is a low hew: An- 

 other record of a note heard in early May reads something like sswink 

 or ssivinkeiy Elsewhere ( 1922) he describes another song : "The song 

 consisted of several repetitions of a high-pitched note with rising 

 inflection, suggesting the goldfish's call note, but less clear and less 

 prolonged, followed by shorter, indefinite notes and then by the roll- 

 ing trill, then more of the high-pitched notes, and so on — a sort of 

 continuous performance, perhaps not always in this precise order, but 

 having the trills interspersed with these long and short notes. The 

 characteristic chatter of the yellow-throated vireo was also thrown 

 in occasionally. The bird dropped this song presently and began 

 its ordinary song." 



E. P. Bicknell (1884) observed one of these vireos singing on the 

 wing : 



On May 21, 1882, I observed a pair flying about among an open group of trees ; 

 one was being followed by the other; but their motions betrayed none of the 

 excitement of pursuer and pursued ; their flight was so easy and leisurely that 

 it was almost restful to watch them. For more than a minute they continued 

 slowly circling about among the trees, within a space of a few rods, passing in 

 and out among the branches ; several times the leading bird appeared about to 

 alight, but feeling its pursuer close at hand continued its course. The rear 

 bird was constantly giving utterance to its full song notes, which fact probably 

 accounts for its uninterested manner as pursuer; for it seemed so engrossed 

 with the feat of singing during flight that it could give little heed to the chase. 

 Both birds Anally alighted peaceably among the branches, the follower alighting 

 first. 



This may have been part of a courtship display, in which the male 

 was showing off his powers of song. 



Albert R. Brand (1938) found that the pitch of the yellow-throated 

 vireo's song was far below the average for passerine birds ; the approxi- 

 mate mean was 2,750, the highest note 3,825 and the lowest 2,325 vibra- 

 tions per second. 



The fact that the yellow-throated vireo has been heard to sing the 

 song of the blue-headed vireo, several times by competent observers, 

 and that the bluehead has been observed to sing the yellowthroat's song, 

 suggests that these two closely related species may occasionally hy- 



