Observations on the Cuckoo. 455 
regular succession, conjectures, that contrary 
to the generality of birds, they have the 
power of retaining the egg in the uterus after 
it is perfected, and that while it remains 
there, the embryo is progressively advanced 
towards maturity by the internal heat of the 
parent’s body.* Now, without having ob- 
served a single circumstance in the whole 
course of my inquiries that at all tended to 
corroborate this opinion of Montagu’s, I have 
discovered a curious fact, which appears to 
render such a supposition altogether unneces- 
sary. Onthe 5th of May, 1822, I saw a 
cuckoo in the act of watching a pair of tit- 
larks construct their nest. The larks had 
just commenced building, and did not seem 
to be at all disconcerted at the presence of 
the cuckoo, which sat on the ground about 
seven or eight yards from the spot, attentively 
observing them; and, when disturbed, flew 
away with great reluctance, and only to a 
short distance. This nest, which was on 
Kersal Moor, where the races are annually 
held, was too distant from my residence to 
permit me to examine it frequently, and to 
make such numerous and minute observations 
as [ wished ; but on the 12th of May I again 
visited it, in the confident expectation that it 
* Ornithological Dictionary, Introduction, p. 15, 
