VOL. LXXVIII.] PHILOSOPHICAL TRANSACTIONS. 433 



great abundance; but like the other migrating birds, she does not begin to lay 

 till some weeks after her arrival. I never could procure an egg till after the 

 middle of May, though probably an early-coming cuckoo may produce one 

 sooner.* 



The cuckoo makes choice of the nests of a great variety of small birds. I 

 have known its egg entrusted to the care of the hedge-sparrow, the water- 

 wagtail, the titlark, the yellow-hammer, the green linnet, and the whinchat. 

 Among these it generally selects the 3 former; but shows a much greater par- 

 tiality to the hedge-sparrow than to any of the rest: therefore, for the purpose 

 of avoiding confusion, this bird only, in the following account, will be considered 

 as the foster-parent of the cuckoo, except in instances which are particularly 

 specified. 



The hedge-sparrow commonly takes up 4 or 5 days in laying her eggs. 

 During this time, generally after she has laid 1 or 2, the cuckoo contrives to 

 deposit her egg among the rest, leaving the future care of it entirely to the 

 hedge-sparrow. This intrusion often occasions some discomposure; for the old 

 hedge-sparrow at intervals, while she is sitting, not unfrequently throws out 

 some of her own eggs, and sometimes injures them in such a way that they 

 become addle; so that it more frequently happens, that only 2 or 3 hedge 

 sparrow's eggs are hatched with the cuckoo's, than otherwise: but whether this 

 be the case or not, she sits the same length of time as if no foreign egg had 

 been introduced, the cuckoo's egg requiring no longer incubation than her own. 

 However, I have never seen an instance where the hedge-sparrow has either 

 thrown out or injured the egg of the cuckoo. When the hedge-sparrow has 

 sat her usual time, and disengaged the young cuckoo and some of her own 

 offspring from the shell,-}- her own young ones, and any of her eggs that remain 

 unhatched, are soon turned out, the young cuckoo remaining possessor of the 

 nest, and sole object of her future care. The young birds are not previously 

 killed, nor are the eggs demolished; but all are left to perish together, either 

 entangled about the bush which contains the nest, or lying on the ground 

 under it. 



The early fate of the young hedge-sparrows is a circumstance that has been 

 noticed by others, but attributed to wrong causes. A variety of conjectures 

 have been formed on it. Some have supposed the parent cuckoo the author of 

 their destruction; while others, as erroneously, have pronounced them smothered 

 by the disproportioned size of their fellow-nestling. Now the cuckoo's egg 



* What is meant by an early-coming cuckoo, I shall more fully explain in a paper on the migra- 

 tion of birds j but it may be necessary to mention here, that migrating birds of the same species 

 arrive and depart in succession. Cuckoos, for example, appear in greater numbers on the 2d than on 

 the 1st week of their arrival, and they disappear in the same gradual manner. — Orig. 



f The young cuckoo is commonly hatched first. — Orig. 



VOL. XVI. 3 K 



