72 OBSERVATIONS ON THE CUCKOO. 
the parent birds would be impelled, by a desire to 
migrate, to quit their progeny before they were able 
to provide for themselves. This hypothesis, as re- 
gards the British species, certainly has an appearance 
of plausibility; yet the early departure of Cuckoos 
may result from their not having to provide susten- 
ance for their young: in what degree it is applicable 
to foreign species, of which Dr. Latham, in his 
‘General History of Birds,’ enumerates about 87, 
besides varieties, is an interesting inquiry which our 
present very imperfect knowledge of their habits and 
economy will not permit us to answer. Dr. Latham, 
indeed, does not particularize more than five or six 
species belonging to this extensive genus which lay 
in the nests of other birds, nor more than twice that 
number which bring up their own young; and of the 
manners and propensities of the rest we are almost 
entirely ignorant. 
Tt is reported that the Cow-pen Bird (Icterus pe- 
coris, Bonaparte), a species perfectly distinct from the 
Cuckoos, has many of their most remarkable peculi- 
arities, intrusting the care of its offspring to strangers, 
and laying only one egg in the same nest. 
Dr. Darwin, in ‘ Zoonomia,’ maintains that the pro- 
pensities of the Cuckoo to lay in the nests of other 
birds and to migrate are not instinctive, and goes so 
far as to reflect upon the reasoning-powers of those 
who entertain a contrary opinion. But the Doctor, 
though a profound scholar and a close observer of 
