206 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



chitinous remains of beetles (one a cerambycid) , lepidopterous larvae, 

 ants and other Hymenoptera, a grasshopper nymph (Melanoplus) , 

 and two balsam needles. 



Sanitation at the nest is scrupulously provided for by the adults. 

 Excreta are picked out of the nest as soon as they appear and imme- 

 diately swallowed. After a few days the young are strong enough to 

 back up to the edge of the nest and deposit the fecal sac on the brim, 

 where it is promptly picked up by one of the parents. Defecation 

 typically takes place right after each feeding, the parent often waiting 

 for the feces and picking them off the elevated cloaca as soon as they 

 appear. As the young grow older, and digestion is perfected, thus 

 reducing the amount of nutritive material in the feces, there is an 

 increasing tendency for the parents to carry the excreta away instead 

 of eating them at the nest. 



Toward the close of the nestling period the young become very 

 active — stretching, preening themselves, jostling, and clambering 

 over one another to attain the topmost position. For some time be- 

 fore actual departure they appear interested in the outside world, 

 peering over the edge of the nest, hopping and walking upon the 

 brim, and even snapping' — usually ineffectively — at passing insects. 

 Naturally birds that are startled into a premature departure, as typ- 

 ically happens at disturbed nests, are not so active as those that re- 

 main the full nestling period. Nine- and ten-day-old birds were 

 relatively quiet prior to their precipitous flight from the nest, but 

 the more normal 11- to 13-day-old birds were very lively during 

 their last days at home. 



Dispersal after nest-leaving is relatively rapid, so that the young 

 usually cannot be located in the vicinity of the nest the following day. 

 They apparently scatter in different directions but are followed and 

 cared for by their parents for an undetermined length of time. 

 Young birds in juvenal plumage are frequently encountered in 

 midsummer, usually only one in a place and attended only by one 

 parent. Later both young and adults become increasingly hard to 

 find, as they enter a quiet period of molting and seclusion that is 

 seldom broken by a fitful outburst of song. 



Plumages. — At birth young thrushes of this form are naked except 

 for wisps of dark gray or blackish natal down along the cephalic, 

 dorsal, and humeral tracts. The other feather tracts (alar, femoral, 

 crural, ventral, and caudal) are not in evidence at birth, even as dark 

 dots beneath the skin, but can plainly be seen by the second and 

 third day, when they contrast sharply with the reddish, blood-suffused 

 apteria. By the third day the quills of the primaries and secondaries 

 are beginning to push through the skin, and on the sixth and seventh 

 days feather tips burst through the ends of the quills. Feather develop- 



