" Stolzmann, who observed them in Peru, says that the
sound caused by the busy crowd searching through the foliage, and the
falling of dead leaves and twigs, resembles that produced by a shower of
rain. The Indians of the Amazons, Mr. Bates writes, have a curious
belief to explain these bird armies; they say that the Papa-uira,
supposed to be a small grey bird, fascinates all the others, and leads
them on a weary perpetual dance through the forest. It seems very
wonderful that birds, at other times solitary, should thus combine daily
in large numbers, including in their bands scores of widely different
species, and in size ranging from those no larger than a wren to others
as big as a magpie. It is certainly very advantageous to them. As Belt
remarks, they play into each other's hands; for while the larger
creepers explore the trunks of big trees, others run over the branches
and cling to the lesser twigs, so that every tree in their route, from
its roots to the topmost foliage, is thoroughly examined, and every
spider and caterpillar taken, while the winged insects, driven from
their lurking-places, are seized where they settle, or caught flying by
the tyrant birds.
I have observed the wandering bands only in Patagonia, where they are on
a very small scale compared with those of the tropical forests. In the
Patagonia thickets the small tit-like creeper, Laptas-thenura, is the
prime mover; and after a considerable number of these have gathered,
creepers of other species and genera unite with them, and finally the
band, as it moves through the thickets, draws to itself other
kinds--flycatchers, finches, &c.
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