196 ClTCULIDvE. 



plied details of great interest on the probable causes which 

 induce the Common Cuckoo, and all other species which 

 deposit their eggs in the nests of small insectivorous birds, 

 not to burthen themselves with the hatching or the feed 

 ing of their young. " The principal cause alleged in the 

 case of the Cuckoo, is the particular nature and effect of 

 its food producing an enlargement of the stomach, which 

 appears to influence the development of the eggs in the 

 ovarium ; these are known to be very small, and the bird 

 lays at intervals of six or eight days." 



Whatever influence may really be attributable to the 

 nature or quantity of the food taken by the Cuckoo, there 

 is good reason to believe that it does produce its eggs at 

 intervals of several days, and this is now known to be the 

 case in the Yellow-billed Cuckoo of America, which does 

 bring up its own young. Four examples of this bird 

 having been shot in this country, it is entitled to a place in 

 this work, and its history will follow in detail ; it may be 

 sufficient here briefly to state that the nests of the Yellow- 

 billed Cuckoo, when examined, contained no two eggs or 

 young birds of the same age ; but all exhibited an obvious 

 difference of several days between their various stages 

 of advancement. 



I have constantly observed, when examining the ana- 

 tomical structure of our Cuckoo, the small comparative size 

 of the parts destined to effect the reproduction of the 

 species. On this subject I furnished a note to Mr. James 

 Jennings, which was published in his Ornithologia in 

 1828. Dr. Jenner, in his paper on the migration of birds, 

 says that he had never found the internal sexual organs of 

 the male Cuckoo so large as those of the Wren, yet the two 

 birds compared in size are as six to one. Mr. Thompson 

 of Belfast, who dissected a female Cuckoo on the 28th of 



