YELLOW-GREEN VIREO 331 



V. -flavomriclis flavoviridis, but to V. flavovwidis insularis, the breed- 

 ing race of the Canal Zone. 



In Costa Rica, the yellow-green vireo sings, in a clear, soft, warbling 



voice, vi't'ee viree viree vireo. The di- 



syllable is the most common phrase, and an indefinite number may 

 be repeated before the trisyllable is uttered. A brief but distinct in- 

 terval separates the phrases. The vireo sings like a true master of 

 the art of happy living — he has taken to heart the doctrine of 7iil 

 nimis of the ancients. He is not, like Gray's thrush, a spendthrift of 

 his music, and is too wise to indulge his delight in song with long- 

 continued, passionate outbursts that drain the cup of melody to the 

 very bottom, and oblige the exhausted songster to pass a period of 

 silence while it slowly fills again, and he has recovered the energy 

 and the mood to sing once more. Eather, he takes his pleasure in 

 sweet sounds with moderation, and lets them escape two or three at 

 a time, with pauses between, that he may continue to utter them 

 through the bright, warm days, and need never be silent because he 

 has indulged to excess his love of singing. 



I have never, to my knoAvledge, heard the female sing, and believe 

 her incapable of song. Her characteristic utterance is a sharp, drawn- 

 out call, which I have sometimes in my notes referred to as a rattle, 

 sometimes as a churr. She also voices a sharp, nasal chaaa. Under 

 the stress of great excitement, both sexes utter harsh, rasping, nasal 

 scolds. 



It is perhaps worthy of note in passing that among the local birds, 

 certain individuals of Cherrie's tanager {Ramphocelus costaricen- 

 sis) — the most songful of our tanagers — deliver a song so similar to 

 that of the yellow-green vireo in tone, phrasing, and long duration 

 that I have sometimes been deceived by it. But as a rule the tanager, 

 a bigger bird, sings in a fuller, more forceful voice than the vireo. 



Field marks. — The yellow-green vireo is easily distinguished, by 

 voice as well as appearance, from other members of the family resi- 

 dent in its Central American breeding range. The red eye, coupled 

 with the light superciliary stripe, is a very good diagnostic character. 

 But for a brief period in spring, as well as in fall, migrating red-eyed 

 vireos mingle with the yellow-green vireos, and then greater acumen 

 is required for correct identification. The best distinguishing marks 

 are the heavier blackish lines bordering the slate-gray crown of the 

 redeye, and the absence on this bird of the yellow which suffuses the 

 sides and under tail coverts of the yellow-green vireo. 



Enemies. — I know of no particular enemies of the adult yellow- 

 gi-een vireo. Doubtless some fall prey to hawks; but I have never 

 witnessed this — indeed, here in El General, I scarcely see two birds 

 captured by hawks in the course of a year. The smaller sets of eggs — 



