pointed feathers which are not
imitated in the Mimeta, although there are signs of faint dusky spots
which may easily furnish the groundwork of a more exact imitation by the
continued survival of favourable variations in the same direction. There
is also a large knob at the base of the bill of the Tropidorhynchus
which is not at all imitated by the Mimeta. In the island of Morty
(north of Gilolo) there exists the Tropidorhynchus fuscicapillus, of a
dark sooty brown colour, especially on the head, while the under parts
are rather lighter, and the characteristic ruff of the nape is wanting.
Now it is curious that in the adjacent island of Gilolo should be found
the Mimeta phaeochromus, the upper surface of which is of exactly the
same dark sooty tint as the Tropidorhynchus, and is the only known
species that is of such a dark colour. The under side is not quite light
enough, but it is a good approximation. This Mimeta is a rare bird, and
may very probably exist in Morty, though not yet found there; or, on the
other hand, recent changes in physical geography may have led to the
restriction of the Tropidorhynchus to that island, where it is very
common.

Here, then, we have two cases of perfect mimicry and two others of good
approximation, occurring between species of the same two genera of
birds; and in three of these cases the pairs that resemble each other
are found together in the same island, and to which they are peculiar.
In all these cases the Tropidorhynchus is rather larger than the Mimeta,
but the difference is not beyond the limits of variation in species, and
the two genera are somewhat alike in form and proportion. There are, no
doubt, some special enemies by which many small birds are attacked, but
which are afraid of the Tropidorhynchus (probably some of the hawks),
and thus it becomes advantageous for the weak Mimeta to resemble the
strong, pugnacious, noisy, and very abundant Tropidorhynchus.

My friend, Mr. Osbert Salvin, has given me another interesting case of
bird mimicry. In the neighbourhood of Rio Janeiro is found an
insect-eating hawk (Harpagus diodon), and in the same district a
bird-eating hawk (Accipiter pileatus) which closely resembles it. Both
are of the same ashy tint beneath, with the thighs and under
wing-coverts reddish brown, so that when on the wing and seen from below
they are undistinguishable. The curious point, however, is that the
Accipiter has a much wider range than the Harpagu