110 BULLETIN 19 6, UNITED STATES NATIONAL MUSEUM 



hatched, or 64 percent. In 1938, of the 51 eggs laid, 43 percent of the 

 young survived to leave the nest. 



In 1937, of the four nests which contained four eggs each, in only 

 one instance did all four young survive to leave the nest. 



In 1938, of eight nests containing four eggs each, in two cases all 

 four young survived, and in one of these two. A cowbird survived 

 with the four young wood thrushes. 



Young. — The first plumage of this species is the natal down, which 

 is light gray in color. Young wood thrushes, at hatching, average 

 5.08 grams in weight. They are approximately 46 millimeters in 

 length; the tarsus averages 17 millimeters; the wing 9 millimeters; 

 and the gape 9 millimeters. On the second day the eye slit breaks 

 through the skin but the eyes are not open. The eyes open between 

 the fifth and seventh days (Brackbill, 1943). On the third day the 

 first feathers, wing primaries, and tail rectrices pierce the skin. The 

 first wing fluttering occurs between the ninth and twelfth days 

 (Brackbill, 1943). 



The female alone broods the young. Brackbill (1943) states that 

 there was no progressive daily decrease in brooding at either of the 

 nests he observed. During the cool hours of early morning the female 

 brooded oftener and for longer periods than during the hotter part of 

 the day. Brooding lasted throughout the nest life of the young even 

 on the day they left the nest. 



Both females on the nest and young wood thrushes were observed 

 to sleep occasionally. The nesting adult would open her eyes quite 

 frequently only to close them again. The young slept both in the 

 nest and after they had left it. On one occasion a young bird that 

 had been out of the nest four days sat for 10 minutes on a small branch 

 with its feathers all fluffed out and its head under its wing. A young 

 bird in the nest was so relaxed during sleep that its head hung down 

 over the edge of the nest. 



Young birds in the nest were marked with small pieces of colored 

 feathers glued to the tops of their heads so that individual records of 

 their activities might be kept. Both male and female birds feed the 

 young in the nest, each bird being fed about every 20 minutes when 

 the birds were seven and eight days old. Young in the nest were fed 

 mulberries and honeysuckle berries as well as animal matter. The 

 food call of nestlings is very weak. It is a single chip in a high- 

 pitched tone. Sometimes the adults gave a squeaky call uttered 

 with the mouth full of food, to get the young to open their mouths. 

 Once the male bird pecked the female on the head to get her to move 

 so he could feed the young. At times the female flew away while the 

 male fed the young, but at other times she stood on the rim of the 

 nest. Both adults disposed of excreta either by swallowing it or by 



