214 On the Natural History of 
necessary data for testing the soundness of the results there given, 
that I propose, in this publication, to treat of such groups more at 
large, rather wishing to lay before the experienced ornithologist the 
reasons upon which my opinions are grounded, than to have it sup- 
posed I wish those opinions to be received upon trust, without the 
production and evidence of facts. 
I believe there cannot be the slightest doubt that the family of the 
Cuculidce or Cuckoos, is the most aberrant family of the scanso- 
rial tribe. This conclusion may be arrived at by two wa.ys,jirst, 
by considering the natural habits and structure of the birds them- 
selves ; and secondly, by ascertaining the relations of affinity which 
they bear to other groups, wherein the scansorial power is more de- 
veloped. The first line of inquiry should always take precedence 
of the second ; because, without understanding the history and 
structure of a bird, it is impossible to associate it with its natural 
companions. !A rapid survey, therefore, of the chief peculiarities of 
the group before us, may precede a more minute inquiry into its 
contents. 
The Cuckoos are altogether natives of such climates as lie beyond 
the influence of frost, and their number seems to be regulated by 
the proximity of their native country to the equator. Thus the 
ornithology of Europe presents us with only two species, both of 
which, during the summer, take up a temporary residence in lati- 
tudes otherwise cold, but which they hastily quit at the approach 
of autumn ; and so congenial is warmth to their nature, that even 
the mild temperature of an Italian winter is not sufficient to retard 
their return to the sultry groves of Northern Africa. There is a 
fact regarding their structure, which appears connected with this 
susceptibility of cold, and which I believe has not hitherto been no- 
ticed. All the Cuckoos, both of the old and the new world, which 
I have had the opportunity of dissecting, are remarkable for the 
thinness and delicacy of their skins, so much so, indeed, as to render 
their preservation in an entire state, extremely difficult to inexpe- 
rienced hands. Every one who has skinned the common British 
species must doubtless have observed this. On the other hand, as 
if to compensate for this delicacy of the cuticle, the feathers, more 
especially upon the back and rump, are unusually thick set and 
compact. Nor is this peculiarity of organization confined to the 
family before us, for we find La Vaillant observing the very same 
thing in respect to the Ceblepyrince of Africa, and nearly the whole 
family of pigeons have very thin skins, and thick set feathers. Nor 
are these relations of analogy without method, for on comparing 
the circles in which the Cuculidce, the Ceblepyrince, and the Colum- 
