A CUCKOO IN A ROBIN'S NEST 17 



sitical Troupials of the genus Molothrus in South 

 America. 



I kept a close watch on the nest for the rest of 

 that afternoon and the whole of the following day 

 (the 28th), during which the young cuckoo was lying 

 in the bottom of the nest, helpless as a piece of jelly 

 with a little life in it, and with just strength enough 

 in his neck to lift his head and open his mouth; 

 and then, after a second or two, the wavering head 

 would drop again. At eight o'clock next morning 

 (29th), I found that one robin had come out of the 

 shell, and one egg had been ejected and was lying 

 a few inches below the nest on the sloping bank. 

 Yet the young cuckoo still appeared a weak, help- 

 less, jelly-like creature, as on the previous day. But 

 he had increased greatly in size. I believe that 

 in forty-eight hours from the time of hatching he 

 had quite doubled his bulk, and had grown darker, 

 his naked skin being of a bluish-black colour. The 

 robin, thirty or more hours younger, was little more 

 than half his size, and had a pale, pinkish-yellow 

 skin, thinly clothed with a long black down. The 

 cuckoo occupied the middle of the deep, cup-shaped 

 nest, and his broad back, hollow in the middle, formed 

 a sort of false bottom; but there was a small space 

 between the bird's sides and the nest, and in this 

 space or interstice the one unhatched egg that still 

 remained and the young robin were lying. 



During this day (29th) I observed that the pressure 



