60 OBSERVATIONS ON THE CUCKOO. 
more than one set of eggs; for Cuckoos come and go 
in succession, some individuals appearing three weeks, 
or even a month, before others ; besides, it may fre- 
quently happen that many females have not an oppor- 
tunity of forming a connexion with the other sex till 
long after their arrival: for though it is generally 
asserted that Cuckoos do not pair, and hence it may 
be inferred that the intercourse between the sexes 
must be greatly facilitated, yet the accurate obser- 
vations of my friend R. G. Baker, Esq., certainly 
render this opinion doubtful. In the spring of 1523 
he noticed that a pair of Cuckoos frequented the same 
spot for more than a fortnight, and were so jealous of 
the approach of any other bird of the same species, 
that they constantly united their efforts to drive away 
an intruder, and always with success. I may add 
that the male was distinguished from every other in 
the vicinity by the deepness of his note. This un- 
questionably looks like pairing, and should, at least, 
prevent a hasty decision on a point which deserves 
further investigation. 
Colonel Montagu, from the extraordinary fact re- 
lated by Dr. Jenner of two Hedge-Warbler’s eggs, 
containing living foetuses, having been found under a 
young Cuckoo about a fortnight old, and from the 
difficulty which he supposes Cuckoos would have in 
meeting with nests in a suitable state to receive their 
eggs, if they were compelled to lay them in regular 
succession, conjectures that, contrary to the generality 
