CUCKOOS IN POSSE 131 



to lay again, if this, which I doubt, is its habit. 

 Thus, after the first retardation in the laying of the 

 one species, consequent upon the action of the other, 

 the two would not be likely again to come into 

 collision ; nor would the woodpecker be seriously 

 injured by being forced, in this way, to become a 

 later-breeding bird. As long as there are a sufficient 

 number of partially-decayed trees for both starlings 

 and woodpeckers and any hole or hollow does for 

 the former I can see no reason why the latter 

 should suffer, except, indeed, in his feelings ; and 

 even if a time were to come when this were no 

 longer the case, why should he not, like the La 

 Plata species, still further modify his habits, even to 

 the extent, if necessary, of laying in a rabbit burrow? 

 Love, I feel confident, would " find out a way." 



But there is another possibility. May not either 

 the woodpecker or the starling be a cuckoo in 

 posse ? If one waits and watches, one may see first 

 the one bird, and then the other, enter the hole, in 

 each other's absence, and it is only when the wood- 

 pecker finds the starling in possession and this, as I 

 am inclined to think, more than once that he 

 desists and retires. Now, the woodpecker having 

 made its nest, is, we may suppose, ready to lay, and, 

 if it were to do so, it is at least possible that the 

 starling might, in some cases, hatch the egg. True, 

 the latter would still have his nest, or a part of it, to 

 make, but it is of loose material straw for the most 

 part and the cow-bird of America has, I believe, 

 been sometimes brought into existence under similar 

 circumstances. Some woodpeckers, too evolu- 

 tion, it must be remembered, works largely through 



