240 The Naturalist in La Plata. 
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 exception- 
ally 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. The Drymornis, a large 
bird, with feet and tail like a woodpecker, climbs on 
tree-trunks to seek its food; but also possesses 
the widely-different habit of resorting to the open 
plain, especially after a shower, to feed on larvae and 
earthworms, extracting them from a depth of three 
