FOSTERERS OF THE CUCKOO 199 
incidents only by accident, and not, as my colleagues 
and myself have, by design. So I have found very 
little indeed that throws light on the way Cuckoos 
deposit their eggs in nests of species such as 
Hedge-sparrows and Reed Warblers, etc. It is 
true that on a good many occasions Cuckoos have 
been seen with an egg in the bill, and observers 
have seemingly jumped to the conclusion that the 
Cuckoos were carrying their own eggs, for no one 
could determine the identity of the egg under such 
circumstances. And in view of the fact, which we 
have been able to establish, that the actual laying 
of the egg can be accomplished within eight 
seconds, is it likely that any one will ever know 
accurately what the exact procedure is, in the 
case of other Cuckoos, unless and until they 
have followed our lead and have so controlled the 
Cuckoo’s operations as to force her to lay in a 
nest appointed for her and have watched her while 
doing so ? 
But there is one piece of evidence that certainly 
points to Cuckoos laying in the nests of Hedge- 
sparrows. In 1920 Miss Hilda Terras produced a 
little book entitled The Story of a Cuckoo's Egg , 
which gave her observations for a season upon a 
pair of Hedge-sparrows victimised by a Cuckoo. I 
