TELLOW-GREEN VIREO 329 



June 1, 1936) lie also failed to bring food. Yet the mother bird was 

 quite capable of attending her nestlings unaided, even on the cool, 

 darkly overcast morning of June 12, when light drizzles alternated 

 with harder showers during most of my 3-hour watch. The two nest- 

 lings, respectively 2 and 3 days old, were kept brooded about two- 

 thirds of the time, from 4 to IT minutes at a stretch, and left exposed 

 for periods ranging from 2 to 8 minutes, while the mother sought 

 food. She was a skillful hunter and frequently returned with some- 

 thing substantial within 2 or 3 minutes after leaving the nest. Many 

 of the winged insects and caterpillars she brought were so big that 

 the tiny nestlings experienced considerable difficulty in swallowing 

 them, and she was obliged to place them several times in the yellow 

 mouths upstretched before her, until at length they disappeared. She 

 kept her babies well filled ; and when, at the end of my watch, they did 

 not readily accept a large insect she brought for them, she swallowed 

 it herself. 



Four days later, when the eldest nestling was a week old, I watched 

 this nest again, and again failed to see the male visit it, although I 

 heard a vireo which was probably the parent singing in the trees 

 along the river. The female still brooded most of the time — TO minutes 

 out of 124 — in periods ranging from 3 to 11 minutes. 



While these nestlings attended by a single parent came safely 

 through the most critical period in their lives, those in the sotacaballo 

 tree beside the Rio San Antonio, whose father was so attentive, met 

 some premature end. Apparently they were attacked and killed by 

 ants, for on the morning of May 19, looking closely through the 

 binoculars, I could discern small ants filing in numbers along the 

 branch to which their nest was attached. Several times the female 

 vireo came and stood beside the nest to pluck from it, in quick succes- 

 sion, a great many small objects invisible to me, doubtless ants. Then 

 she would fly off again, uttering her sharp little rattle. Once the 

 father vireo came with an insect in liis bill, singing as was his custom, 

 and stood for a few moments above the nest, continuing to sing. At 

 length he carried the insect off and swallowed it and went on singing 

 as before. But during the course of an hour the nestlings were neither 

 fed nor brooded, whence I inferred that they were dead. So much 

 attention given to a nest with dead nestlings implies lack of insight 

 on the part of the parents; but "what should they know of death?" 



Despite the apparent security of the cobweb bindings that attach 

 the rim of the nest to the arms of the crotch in which it hangs, it not 

 infrequently becomes detached, on one or both sides, before the young 

 are feathered, or even before the eggs have hatched. On several oc- 

 casions, I have saved the occupants from disaster by sewing or tying 

 up the nest. Though hummingbirds reinforce the bindings of their 



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