NOTES AND QUERIES. 



deposited therein by the foster-parents. Occasionally the egg of the 

 Cuckoo is the only egg found within the nest, but the probability is 

 that the first egg of the foster-parent had already been removed. 

 Again, I know the Cuckoo will deposit its egg several days after the 

 foster-parents have started incubation, but what is known of the 

 longest time allowed to elapse before so doing ? Personally I believe 

 this time is limited ; if so, we must credit the Cuckoo with an instinct 

 of knowing to what extent incubation has already taken place. The 

 incubation of the egg of the Cuckoo is evidently more rapid than the 

 eggs of the usual foster-parents, giving the dual advantage to the 

 young Cuckoo of being hatched first, or, if the eggs had been 

 deposited after the foster-parent had commenced to sit, then of being 

 hatched at least about the same time. The same species of foster- 

 parents are not invariably chosen by each individual Cuckoo, but, on 

 the other hand, I believe the Cuckoo does frequently restrict itself 

 to one kind of foster-parent as far as possible, so much so, as to 

 considerably retard the time of its laying, as, for instance, when using 

 the nest of the Eeed- Warbler, which would be weeks after eggs of 

 other Cuckoos had been deposited in such nests as the Pied Wagtail, 

 Hedge- Sparrow, Eobin, or Meadow-Pipit. And further, the Cuckoos 

 that utilize the former nests are necessarily delayed in their return 

 migration. I have recorded an instance (' Zoologist,' July, 1915, 

 p. 270) of the Cuckoo laying four eggs all in the nests of Eeed- 

 Warbler, and I have known several instances where the same bird 

 has laid at least several eggs in the nests of the same species of 

 foster-parents ; and, again, where one Cuckoo had selected nests of 

 various kinds of foster-parents — in one instance a Greenfinch, Brown 

 Linnet, and Chaffinch being chosen. How many eggs of the foster- 

 parent are usually removed by the Cuckoo, and what actually becomes 

 of them ? In my experience I have only known two nests, those of 

 a Sedge- Warbler and a Hedge- Sparrow, where I knew the complete 

 clutch of the foster-parent was left intact, and such exceptions may 

 prove nothing more than that the Cuckoo had been disturbed before it 

 had time to carry out its full intentions. As a rule I believe at least 

 one and often two eggs are removed and possibly three, but I have no 

 actual proofs to support the latter statement. That the Cuckoo can 

 lay a type of egg to assimmilate to those of the foster-parents has often 

 been asserted, but all my personal experience has been that the one 

 female shows a remarkable similarity in each of her eggs, irrespective 

 of the foster-parents, and, moreover, this similarity is continued 

 year by year. And, further, the young of the Cuckoo inherits to a 



