212 THE GYPSY MOTH. 



Yellow-billed Cuckoo. In 1891 yellow-billed cuckoos 

 were observed in several of the worst infested localities, 

 where they remained nearly all day, feeding on the gypsy 

 larvae or carrying them from time to time to their young. 

 This habit of feeding on hairy larvae seems to be quite con- 

 stant with the cuckoos. They seem to prefer the gypsy 

 larvae even to the pupae. 



Mr. F. H. Mosher, an inspector in the employ of the 

 Board, who observed this species in 1895, says that it will 

 go to a bunch of pupae and search for larvae, pulling out the 

 molts or casts, and will take pupae only when larvae are not 

 to be found. This was noticed in different individuals of 

 this species and in different localities. Some of the cuckoos 

 would take no pupae at all, but would continue their search 

 for larvae until they found them. 



That the yellow-billed cuckoos feed their young quite con- 

 stantly on these larvae is evident from the observations made. 

 The stomach of one young cuckoo when examined contained 

 a number of partly digested larvae and the heads of sixteen 

 others. Ninety per cent, of the stomach contents consisted 

 of these larval remains. When the young birds were able to 

 fly, the parents would lead them to the worst infested spots 

 and feed them frequently with caterpillars. 



Mr. C. E. Bailey, an agent of the Board and a field orni- 

 thologist of much experience, says that the yellow-billed 

 cuckoo is very fond of the gypsy larvae, sometimes eating 

 nine or ten full-grown ones in less than a half hour. He 

 also states that he has observed that it eats more caterpillars 

 than the black-billed cuckoo. 



Black-billed Cuckoo. The black-billed cuckoo is probably 

 nearly if not quite as useful as its congener in destroying 

 hairy caterpillars, and appears to be almost equally destruc- 

 tive to the gypsy moth larvae. From personal observation, 

 as well as from reports of the observations of others, I am 

 led to believe that this bird does not feed as rapidly as the 

 yellow-billed cuckoo, and spends more time in beating the 

 caterpillars, perhaps for the purpose of killing them, or pos- 

 sibly to divest them of their hairs before eating them. In 

 the end, however, the caterpillar is swallowed whole. Like 

 the yellow-billed cuckoo, this species feeds the caterpillars 

 to its young. 



