In a majority of cases, however, the colour is undoubtedly
protective, the brown hue being of a shade that assimilates very closely
to the surroundings. There are pale yellowish browns, lined and mottled,
in species living amidst a sere, scanty vegetation; earthy browns, in
those frequenting open sterile or stony places; while the species that
creep on trees in forests are dark brown in colour, and in many cases
the feathers are mottled in such a manner as to make them curiously
resemble the bark of a tree. The genera Lochmias and Sclerurus are the
darkest, the plumage in these birds being nearly or quite black, washed
or tinged with rhubarb yellow. Their black plumage would render them
conspicuous in the sunshine, but they pass their lives in dense tropical
forests, where the sun at noon sheds only a gloomy twilight.
If "colour is ever tending to increase and to appear where it is
absent," as Dr. Wallace believes, then we ought to find it varying in
the direction of greater brightness in some species in a family so
numerous and variable as the Dendrocolaptidae, however feeble and in
need of a protective colouring these birds may be in a majority of
pases. And this in effect we do find. In many of the dark-plumaged
species that live in perpetual shade some parts are a very bright
chestnut; while in a few that live in such close concealment as to be
almost independent of protective colouring, the lower plumage has become
pure white.
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