Analogous Facts Have Been Observed By Dr.
Richardson In North America.
Of land-birds I obtained twenty-six kinds, all peculiar to
the group and found nowhere else, with the exception of one
lark-like finch from North America (Dolichonyx oryzivorus),
which ranges on that continent as far north as 54 degs., and
generally frequents marshes.
The other twenty-five birds
consist, firstly, of a hawk, curiously intermediate in structure
between a buzzard and the American group of carrion-feeding
Polybori; and with these latter birds it agrees most
closely in every habit and even tone of voice. Secondly,
there are two owls, representing the short-eared and white
barn-owls of Europe. Thirdly, a wren, three tyrant-flycatchers
(two of them species of Pyrocephalus, one or both of
which would be ranked by some ornithologists as only varieties),
and a dove - all analogous to, but distinct from, American
species. Fourthly, a swallow, which though differing
from the Progne purpurea of both Americas, only in being
rather duller colored, smaller, and slenderer, is considered
by Mr. Gould as specifically distinct. Fifthly, there are three
species of mocking thrush - a form highly characteristic of
America. The remaining land-birds form a most singular
group of finches, related to each other in the structure of
their beaks, short tails, form of body and plumage: there are
thirteen species, which Mr. Gould has divided into four
sub-groups. All these species are peculiar to this archipelago;
and so is the whole group, with the exception of one species
of the sub-group Cactornis, lately brought from Bow Island,
in the Low Archipelago. Of Cactornis, the two species may
be often seen climbing about the flowers of the great cactus-
trees; but all the other species of this group of finches,
mingled together in flocks, feed on the dry and sterile ground
of the lower districts. The males of all, or certainly of the
greater number, are jet black; and the females (with perhaps
one or two exceptions) are brown. The most curious fact is
the perfect gradation in the size of the beaks in the different
species of Geospiza, from one as large as that of a hawfinch
to that of a chaffinch, and (if Mr. Gould is right in including
his sub-group, Certhidea, in the main group) even to
that of a warbler. The largest beak in the genus Geospiza
is shown in Fig. 1, and the smallest in Fig. 3; but instead of
there being only one intermediate species, with a beak of
the size shown in Fig. 2, there are no less than six species
with insensibly graduated beaks. The beak of the sub-group
Certhidea, is shown in Fig. 4. The beak of Cactornis is
somewhat like that of a starling, and that of the fourth
sub-group, Camarhynchus, is slightly parrot-shaped. Seeing this
gradation and diversity of structure in one small, intimately
related group of birds, one might really fancy that from an
original paucity of birds in this archipelago, one species had
been taken and modified for different ends.
Enter page number
PreviousNext
Page 303 of 402
Words from 156390 to 156916
of 208183
