Hence the Adrianic fowls lay most eggs,
for because of the smallness of their bodies the nutriment is used
up in producing young. And other birds are more fertile than
game-fowl, for their bodies are more fluid and bulkier, whereas
those of game-fowl are leaner and drier, since a passionate spirit
is found rather in such bodies as the latter. Moreover the thinness
and weakness of the legs contribute to making the former class of
birds naturally inclined to tread and to be fertile, as we find also
in the human species; for the nourishment which otherwise goes to
the legs is turned in such into a seminal secretion, what Nature takes
from the one place being added at the other. Birds of prey, on the
contrary, have a strong walk and their legs are thick owing to their
habits, so that for all these reasons they neither tread nor lay much.
The kestrel is the most fertile; for this is nearly the only bird of
prey which drinks, and its moisture, both innate and acquired, along
with its heat is favourable to generative products. Even this bird
does not lay very many eggs, but four at the outside.
The cuckoo, though not a bird of prey, lays few eggs, because it
is of a cold nature, as is shown by the cowardice of the bird, whereas
a generative animal should be hot and moist. That it is cowardly is
plain, for it is pursued by all the birds and lays eggs in the nests
of others.
The pigeon family are in the habit of laying two for the most
part, for they neither lay one (no bird does except the cuckoo, and
even that sometimes lays two) nor yet many, but they frequently
produce two, or three at the most generally two, for this number
lies between one and many.
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