ANOTHER COMMON (1921) 165 
might lay in Meadow Pipits’ nests on the common, 
since we required these eggs to illustrate the 
season’s story. So we brought eggs from a distance 
and put them down in Meadow Pipits’ nests our- 
selves. On June 10 we put a Cuckoo’s egg from a 
Hedge-sparrow’s {Accentor modnlaris ) nest into a 
Meadow Pipit’s nest with five eggs, removing two 
of the latter in exchange. On the evening of 
June 12 we found a three days’ incubated Cuckoo’s 
egg in another Hedge-sparrow’s nest with four eggs, 
and exchanged it for the one we had used on the 
10th, as we had reason to fear that it might be 
addled. On June 22 the Meadow Pipit’s eggs 
hatched, and on the 24th I removed the still un- 
hatched Cuckoo’s egg, thinking that it was now no 
good. On blowing it, I found that it contained a 
live youngster. On comparing the eggs subse- 
quently I found it to be a different egg from that 
transferred from the Hedge-sparrow’s nest, and 
identical with another Cuckoo’s egg N 2 found on 
June 20 in a Meadow Pipit’s nest near by. Subse- 
quent to our putting the Hedge-sparrow Cuckoo’s 
egg in the nest on June 12, Cuckoo N must have 
laid in the nest and removed the Cuckoo’s egg we 
had inserted. The Cuckoo’s first act on ap- 
proaching a nest to lay being the removal of one 
