A NATURAL HISTORY OF THE CUCKOO. 53 
to which the enormous pectoral muscles, those which constitute 
what is termed the breast-cut in a Fowl, and the contraction of 
which imparts the propulsive stroke in flying, are attached—being 
less developed, and the wing-bones shorter. The similitude of their 
alimentary organs is also considerable ; and both are remarkable for 
the diminutive size of the brain, which in the Cuckoo barely out- 
weighs a single eye (being only about twenty grains), and in the 
Moth-hunter is reduced to its minimum in the class of birds. 
There are certain other resemblances observable, but on the present 
occasion I deem it unnecessary to pursue the subject further. 
Both the Cuckoos and the Moth-hunters pertain to that ex- 
tensive order of birds which, in an arrangement of the class which 
I had lately the honour of submitting to the Zoological Society, 
I designated Strepitores, (or Screechers) ; an order characterized 
by numerous physiological agreements, but which embraces many 
forms externally dissimilar—that is to say, in those adaptive cha- 
racters which have reference to a special mode of life. It is only 
in this group, among what have been termed perching birds, that 
the vocal organ is simple, or furnished with only a single pair of 
muscles ; in consequence of which its various members are unable 
to inflect the voice, and can only utter some peculiar cry, as we ob- 
serve in the Cuckoo. Now, throughout the long series of groups 
which compose this order—that is to say, in all those Insessores of 
Mr. Vigors’ arrangement which have a simple vocal apparatus, the 
brain is less highly organized than in the contiguous ordinal divi- 
sions ; and there is a corresponding marked inferiority in the intel- 
lectual capacity ; for while the extreme docility of the Parrots, and 
of the Crows, Finches, &c. is notorious to every one, I am unaware 
that a single instance can be adduced of any species belonging to the 
distinct order adverted to, manifesting the least capability of receiv- 
ing instruction. It is true that they may be tamed, may exhibit at- 
tachment to one person more than to another, that some of them, at 
least, will readily distinguish those they are accustomed to, while 
they evince distrust of a stranger ; but I am greatly mistaken if any 
one of them could be trained to any purpose, could be taught to 
perform a single action that is not natural to them. Whoever has 
observed a Kingfisher, a Cuckoo, or a Woodpecker, in a state of 
captivity, will readily acknowledge the force of this remark. 
With respect to those genera which have been commonly more 
immediately associated with the Cuckoos, it will be sufficient to 
remark that the genus Cuculus of Linneus comprehended several, 
which have sinee been separated with propriety, though still brought 
