39-4 BIRDS OF ILLINOIS. 



Jamaica specimens, which also are smaller; northern specimens, 

 however, show similar variations. In the immature birds the under 

 surface of the tail-feathers is gray, not black, so that the contrast 

 with the white tips is very indistinct, as in erythrophthafavus, in 

 which, however, these light tips are much narrower, while the bill 

 is entirely black. 



This bird, familiarly known as the Kain Crow, Wood Pigeon, or 

 Cow-cow, is a summer resident of all portions of the State, though 

 more abundant southward, its range being to some extent comple- 

 mentary to that of the black-billed species, which is more common 

 northward. 



While habitually building its own nest, and caring for its young, 

 this species as well as C. eryth/rophthahnuB occasionally not only 

 impose on one another, but also, though more rarely, upon other 

 birds. Of this fact there is much indisputable evidence on record. 

 It is also a well-known fact that in nests of both these species it 

 is not an uncommon thing to find not only eggs in different stages 

 of incubation but also young and freshly laid eggs in the same 

 nest. Colonel S. T. Walker, of Milton, Florida, writes to Professor 

 Baird that he has found young birds in the nest just ready to fly, 

 others half fledged, and some just hatched, and at the same time 

 one or two fresh eggs. He is not sure whether other Cuckoos lay 

 in the same nest or whether the same bird continues to lay while 

 setting. From what he has seen, however, he is inclined to believe 

 that the latter is the case, and that "the old bird utilizes the warmth 

 of the young first hatched to continue the incubation of eggs sub- 

 sequently laid." 



Eegarding this point it may be stated that the parasitic habit of 

 the European Cuckoo (Cuculus canorus) is supposed to result from 

 the very slow development of the eggs in the oviduct, rendering it 

 practically impossible for themselves to attend to the incubation of 

 then: eggs ; and it may be suggested that the circumstances to which 

 Col. Walker alludes, and which have been noted by other observers, 

 arise from the same cause. Furthermore since, as stated above, it 

 is known also that both the American Cuckoos occasionally drop 



