Another curious variation is found in Sylviothorhynchus, a small
wren-like bird and the only member known of the genus, with a tail
resembling that of the lyre-bird, the extravagantly long feathers being
so narrow as to appear almost like shafts destitute of webs. This tail
appears to be purely ornamental.
This extreme variety in structure indicates a corresponding diversity in
habits; and, assuming it to be a true doctrine that habits vary first
and structure afterwards, anyone might infer from a study of their forms
alone that these birds possess a singular plasticity, or tendency to
vary, in their habits--or, in other words, that they are exceptionally
intelligent; and that such a conclusion would be right I believe a study
of their habits will serve to show.
The same species is often found to differ in its manner of life in
different localities. Some species of Xenops and Magarornis, like
woodpeckers, climb vertically on tree-trunks in search of insect prey,
but also, like tits, explore the smaller twigs and foliage at the
extremity of the branches; so that the whole tree, from its root to its
topmost foliage, is hunted over by them. The Sclerurus, although an
inhabitant of the darkest forest, and provided with sharply-curved
claws, never seeks its food on trees, but exclusively on the ground,
among the decaying fallen leaves; but, strangely enough, when alarmed it
flies to the trunk of the nearest tree, to which it clings in a vertical
position, and, remaining silent and motionless, escapes observation by
means of its dark protective colour.
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