The Descent of Man and Selection in Relation to Sex, Vol. IDarwin, Charles
Science
The Descent of Man and Selection in Relation to Sex, Vol. I
Darwin, Charles
Evolution (Biology); Human beings -- Origin; Sex differences; Sexual dimorphism (Animals); Sexual selection in animals
With respect to birds in a state of nature, Mr. Gould and
others[379] are convinced that the males are generally the more
numerous; and as the young males of many species resemble the
females, the latter would naturally appear to be the most
numerous. Large numbers of pheasants are reared by Mr. Baker of
Leadenhall from eggs laid by wild birds, and he informs Mr.
Jenner Weir that four or five males to one female are generally
produced. An experienced observer remarks[380] that in
Scandinavia the broods of the capercailzie and black-cock
contain more males than females; and that with the Dal-ripa (a
kind of ptarmigan) more males than females attend the _leks_ or
places of courtship; but this latter circumstance is accounted
for by some observers by a greater number of hen birds being
killed by vermin. From various facts given by White of
Selbourne,[381] it seems clear that the males of the partridge
must be in considerable excess in the south of England; and I
have been assured that this is the case in Scotland. Mr. Weir
on enquiring from the dealers who receive at certain seasons
large numbers of ruffs (_Machetes pugnax_) was told that the
males are much the most numerous. This same naturalist has also
enquired for me from the bird-catchers, who annually catch an
astonishing number of various small species alive for the
London market, and he was unhesitatingly answered by an old and
trustworthy man, that with the chaffinch the males are in large
excess; he thought as high as 2 males to 1 female, or at least
as high as 5 to 3.[382] The males of the blackbird, he likewise
maintained, were by far the most numerous, whether caught by
traps or by netting at night. These statements may apparently
be trusted, because the same man said that the sexes are about
equal with the lark, the twite (_Linaria montana_), and
goldfinch. On the other hand he is certain that with the common
linnet, the females preponderate greatly, but unequally during
different years; during some years he has found the females to
the males as four to one. It should, however, be borne in mind,
that the chief season for catching birds does not begin till
September, so that with some species partial migrations may
have begun, and the flocks at this period often consist of hens
alone. Mr. Salvin paid particular attention to the sexes of the
humming-birds in Central America, and he is convinced that with
most of the species the males are in excess; thus one year he
procured 204 specimens belonging to ten species, and these
consisted of 166 males and of 38 females. With two other
species the females were in excess: but the proportions
apparently vary either during different seasons or in different
localities; for on one occasion the males of _Campylopterus
hemileucurus_ were to the females as five to two, and on
another occasion[383] in exactly the reversed ratio. As bearing
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account