108 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



sions are drawn from observations on two closely watched nests of 

 four eggs each. Eggs were marked. The first two eggs in each case 

 hatched in 14 days and the last two in 13 days. 



The brood spot occupies the region of the abdomen. It is deep 

 red in color and is devoid of all feathers. This was found only on 

 female birds and was used to identify the females when banding them. 



The eggs were turned by the female by clasping the egg between 

 the angle made by the bill, chin, and throat when the head was 

 pointed downward into the nest. With a raking motion she turned 

 the eggs. 



Incubation is performed solely by the female wood thrush. In 

 order to prove this, a unique method of catching nesting birds was 

 employed. William Montagna had learned this in Italy. At the 

 time of this study he was assistant to Dr. G. M. Sutton, of the Labo- 

 ratory of Ornithology of Cornell University. He employed a piece 

 of orchard grass 2% feet long. The leaves were stripped from it and 

 a slip knot was tied at the end. The grass was moved up to the bird 

 on the nest without frightening her. It was slipped over her head and 

 tightened, and the nesting bird was captured. These birds were 

 then marked with colored feathers, as well as aluminum bands, for 

 identification purposes. Since no desertions resulted, the method was 

 considered successful. Subsequent visits to the nests of birds marked 

 in this fashion and observations on other banded birds give evidence 

 of the fact that only the female incubates. Several birds were trapped 

 with a drop trap as the young were about to leave the nest. Only 

 one bird of each pair had a brood spot. Examination of the gonads of 

 a bird, believed to be the male of a pair with young in the nest, indi- 

 cated that the bird on the nest was the female. Brackbill (1943) also 

 states that only the female incubates. His study was made with 

 marked birds. 



I should like to describe the hatching of eggs by giving an account 

 of an all-day observation period beginning at 4:10 A. m. on June 22, 

 1937, in Ithaca, N. Y. The female sat deeply huddled in the nest. 

 The male was singing soon after 4 a. m. From this time until 7:15 

 a. m. the female would raise herself from the nest, back off, and look 

 in. Sometimes she would peck in the nest, then settle on again with 

 a rolling motion. She repeated this over a period of four hours on the 

 average of once every 15 minutes. At 9:15 a. m. her anxiety was 

 relieved by the hatching of one of her four eggs. Male birds of this 

 species had not been observed to feed the female on the nest, and so 

 it was thought that perhaps the male in this case was acting in antici- 

 pation of the coming event when he arrived at the edge of the nest in 

 the absence of the female with a small green caterpillar dangling from 

 his mouth. He stood on the edge of the nest, looked in, ate the cater- 



