122 The Wilson Bulletin — No. 84. 



the crotch of a gray birch, formed by the bole of a sapling 

 and a rudimentary branch about three feet above the ground. 

 The nest was surrounded by fir branches. Each day an egg 

 was added to the set until there were four. The afternoon 

 that the clutch was completed, when I approached the nest, 

 the bird was quite oblivious of every duty save that of incu- 

 bation. She seemed unaware of my presence. Until this time 

 I did not see the bird around the nest, yet the eggs hatched, 

 as before intimated, at very irregular intervals. 



The eighth day of incubation I placed the blind in the 

 neighborhood of the nest, that the birds might get accustomed 

 to it. On the tenth day, when I went to observe at the blind, 

 the female was off the nest ; I peeped in. and to my astonish- 

 ment, beheld two young birds on which the natal down was 

 entirely dry. The next morning at 9 :30 there were three 

 nestlings in the nest, and at 5 :00 p. m. the fourth egg was 

 still unhatched. On the twelfth day of incubation^ at 11 ".oo 

 a. m., there was a fourth young Thrush in the nest on which 

 the natal down was not entirely dry. 



I have studied no other bird whose eggs were hatched so 

 irregularly, save the Black-billed Cuckoo. The Cuckoo be- 

 gins to incubate as soon as an egg is laid, and does not al- 

 ways lay on consecutive days.^ 



In the case of the Olive-backed Thrush, the fact that the 

 young came from the egg at such long intervals, seemed to 

 be a wise provision of nature. The mother bird brooded the 

 young, except during the rest period, for the greater part of 

 the time during the first three or four days. She moved back 

 on the nest, stood astride the young, and cared for one fragile 

 chick at a time ; she pecked him and touched him with her 

 beak until he gave the food reaction readily, fed him by re- 

 ijuly 11, 1908, I found the nest of a Blaek-billed Cuckoo con- 

 taining two eggs. The bird was brooding. Two days later there- 

 was a third egg. As nearly as I could determine, the three eggs 

 were hatched on two consecutive days. The two older birds left 

 the nest at the beginning of the climbing period, and the parents,, 

 it would seem, devoted themselves to the mature nestlings. I. 

 found the youngest dead in the nest after a rain storm. 



