332 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



two or three instead of the three to five of the red-eyed vireo, and a 

 breeding season scarcely longer — indicate that the shorter migra- 

 tions of this species are accomplished with fewer losses than the long 

 flights of its northern relative. 



The nests are sometimes — probably very frequently — pillaged by 

 snakes. On May 22, 1910, while passing near a nest situated about 6 

 feet above ground on a drooping branch of a sotacaballo tree be- 

 side the Rio Pacuar, I found the parents very much excited, uttering 

 their nasal rasping scolds with great vehemence. Examination re- 

 vealed the nest empty ; but with a little searching I found, in the grass 

 below, a small green snake with a partly feathered nestling in its 

 mouth, already dead. After killing the serpent, I discovered the 

 second nestling in the grass close by, and returned it to its nest. Had 

 the nestlings jumped from the nest at the snake's approach, and the 

 reptile then dropped upon them? As I was about to depart, I espied 

 a second snake, brown and much larger, in the bushes below the 

 same tree, on the bank of the river. It had doubtless been attracted 

 by the commotion and would probably have devoured the second 

 nestling if this had escaped the green snake — and possibly the smaller 

 green serpent too. 



A very different sort of destroyer of the vireo's eggs and nestlings 

 is Swainson's toucan {Rhamphastos sivainsonii) . During the months 

 when most of the smaller birds are nesting, parties of these huge-billed 

 birds fly from the forest into the scattered trees of the pastures and 

 plantations, filling the breeding birds with rage and dismay. Their 

 arrival is heralded by the calls of alarm and distress of anxious parents ; 

 their progress marked by the darting forms of indignant flycatchers ; 

 and wherever they pass they leave a trail of rifled bird nests. It is 

 probable that the swallow-tailed kite also devours the nestlings of the 

 yellow-green vireo, for I have seen it pillage nests of other birds that 

 breed in the same trees. 



Once, on a coffee plantation on the Pacific slope of Guatemala, an 

 Indian, misunderstanding my request that he take me to see any nests 

 he might find, brought me one of the yellow-green vireo, containing 

 three half -grown vireo nestlings, and one of the red-eyed cowbird. 

 All were in a flourishing condition, and but for their unfortunate 

 removal, the vireo nestlings might have been raised beside their foster- 

 brother as sometimes happens with the red-eyed vireo. Although I 

 returned the nest to the tree where the man said it had been found, 

 next morning all four nestlings were dead. 



Fall. — Southern Costa Rica is probably the wettest district on the 

 generally dry Pacific side of the American Continent between Wash- 

 ington and Colombia. Here, where June is usually a period of heavy 

 rainfall, the yellow-green vireos cease nesting in this month. My 



