Shell of Cuckoo's Egg. 127 



hammer's nest on July 3rd, and of a young cuckoo 

 unable to fly on the 28th July last." 



Further yet : Mr. Rowley (Ibis, 1865, pp. 178-9) 

 says that, from personal observation, he believes the 

 period of laying to begin in the beginning of May 

 and to go on at least to the middle of July, he having 

 taken eggs of the cuckoo's as late as on the 29th of that 

 month. 



In certain seasons, in certain parts from which the 

 cuckoos migrate early — that is, in the latter part of 

 July — it is, of course, impossible that, in the case of 

 eggs laid so late as to show young cuckoos only a 

 short time before the 28th July, and eggs taken from 

 nests on the 29th, the elder cuckoos should be able to 

 do the service of removing the companion foster- 

 parents' eggs, and, still more, the young ones, after 

 their hatching, which generally follows that of the 

 cuckoo — the cuckoo's eggs, like the eggs of the 

 American molothrus or cow-bird, as we shall see 

 afterwards in the proper place, needing shorter in- 

 cubation by some days than those of the victimised 

 birds — another most remarkable fact in the economy 

 of the bird, more especially considering the thickness, 

 and hardness, and heaviness of shell of the cuckoo's 

 Qgg. The cuckoo's egg, indeed, contains the shell 

 matter requisite for an egg the normal size of the 

 bird, and the contents are, so to say, concentrated.''' 



And here arises another question. Many of those 

 who wish — following Jenner — to shorten the period of 

 the cuckoo's sojourn here as much as they possibly can, 

 in order to gain one point in their favour, have also 

 to show how in this case the young foster-birds are 



* Miller's Essays and Nature Studies, p. 59. 



