Birds are equally well protected by assimilative hues; the
larks, quails, goatsuckers, and grouse which abound in the North African
and Asiatic deserts are all tinted or mottled so as closely to resemble
the average colour of the soil in the districts they inhabit. Canon
Tristram, who knows these regions and their natural history so well,
says, in an often quoted passage: "In the desert, where neither trees,
brushwood, nor even undulations of the surface afford the slightest
protection to its foes, a modification of colour which shall be
assimilated to that of the surrounding country is absolutely necessary.
Hence, without exception, the upper plumage of every bird, whether lark,
chat, sylvain, or sand-grouse, and also the fur of all the smaller
mammals, and the skin of all the snakes and lizards, is of one uniform
isabelline or sand colour."
Passing on to the tropical regions, it is among their evergreen forests
alone that we find whole groups of birds whose ground colour is green.
Parrots are very generally green, and in the East we have an extensive
group of green fruit-eating pigeons; while the barbets, bee-eaters,
turacos, leaf-thrushes (Phyllornis), white-eyes (Zosterops), and many
other groups, have so much green in their plumage as to tend greatly to
their concealment among the dense foliage.
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