FIRST SEASON (1918): RECORD 21 
habit first to seek out, by the process of watching 
its dupes, the nests suitable for its eggs, and, having- 
done so, to lay its eggs on dates that coincide 
with those on which the nest is in a favourable 
condition. 
From the study I had made of other species, 
particularly of the Red-backed Shrike ( Lanins 
collurio , L.), I had proved conclusively that if a nest 
be destroyed the bird will almost immediately 
begin to build another nest and will often lay the 
first egg of its new clutch on the fifth or even the 
fourth morning after losing its first nest. This 
being an ascertained fact, it seemed to me probable 
that a Cuckoo was quite likely to develop its eggs 
within four or five days after finding the nests of 
its dupes in the process of being built. We shall 
see later how this theory eventually proved to be 
in the main correct. 
On June 30 I found the only Meadow Pipit’s 
nest which came under my observation that did not 
ultimately contain an egg of either of the Cuckoos 
frequenting the common. 
Being anxious to make the results of the season 
as complete as possible, I devoted July 5, 6, and 7 
to a comprehensive search. I found that I had 
missed one nest, for on the evening of the 6th w r e 
