YELLOW-GREEN VIREO 327 



not drop them to the ground. Accordingly, to get rid of them, she was 

 obliged to wipe them onto the branch beside the nest. She always sat 

 in the same position, facing the crotch, and invariably attached the 

 seeds to the branch on her left, with the result that a conspicuous mass 

 of them had accumulated here. As she placed another seed on the 

 mass and withdrew her head, a string of slime would frequently pull 

 out between her bill and the seed, so viscous was the substance sur- 

 rounding it. The newly attached seeds would sometimes slip down 

 over the older ones, to remain adhering to the lower side of the lowest, 

 thus forming short, beadlike chains. Wliile the vireo regurgitates 

 these mistletoe seeds, they pass entirely through the alimentary tract 

 of euphonias, and retaining their adhesive properties as well as their 

 viability, stick to the branches and germinate, to the great detriment 

 of the trees. 



The ever-growing mass of seeds seemed to annoy the vireo, and 

 she devoted considerable effort to keeping it small. Frequently, while 

 sitting, she plucked off the seeds in her bill, whence she was able to 

 drop many of the older ones upon which the gum had dried ; but others 

 clung so stubbornly that she was constrained to attach them to the 

 mass again in order to free herself of the incumbrance. At times she 

 ate seeds that she had previously attached to the mass ; at other times 

 she swallowed again those which had just slipped up into her mouth. 

 Upon leaving the nest for a recess, she almost always carried away a 

 seed, either one newly regurgitated, or one plucked from the mass at 

 her side. Not infrequently she made trips to the nest during her recess 

 for the purpose of carrying away these seeds. On these visits she 

 usually plucked a single seed from the cluster and flew off with it, 

 but on one occasion she swallowed one seed and carried a second in 

 her bill. During the course of a single recess, she made four visits to 

 the nest, and carried away five seeds. 



The viscous substance surrounding the mistletoe seeds appeared to 

 be somewhat attractive to insects ; and I saw the vireo Vvdiile incubating 

 eat two flylike creatures which had stuck to the cluster. Thus there 

 was a certain advantage to the bird in this mass of gummy seeds, for 

 it brought food directly to her mouth as she warmed her eggs. 



Young. — The incubation period, as determined at two nests, is 14 

 days. The pink-skinned nestlings have their eyes tightly closed. At 

 first glimpse they appear to be quite naked; but careful scrutiny in a 

 favorable light reveals a few scattered tufts of very short, fine down 

 on the top of the head, back, and wings. The interior of the mouth is 

 yellow, as in the majority of insectivorous passerine birds. 



As a rule the nestlings are fed by both parents. If he has been 

 attentive during the course of incubation, the male may begin to bring 

 food quite promptly after the eggs have hatched. This was so of the 



