each other only in their climbing feet; in the form of their beaks they
are as wide apart as are nuthatches, woodpeckers, crows, and curlews.
They also differ markedly in the manner of seeking their food. Some dig
like woodpeckers in decayed wood; others probe only in soft rotten wood;
while the humming-bird-billed Xiphorhynchus, with a beak too long and
slender for probing, explores the interior of deep holes in the trunks
to draw out nocturnal insects, spiders, and centipedes from their
concealment. Xiphoco-laptes uses its sword-like beak as a lever,
thrusting it under and forcing up the loose bark; while Dendrornis, with
its stout corvine beak, tears the bark off.

In the nesting habits the diversity is greatest. Some ground species
excavate in the earth like kingfishers, only with greater skill, making
cylindrical burrows often four to five feet deep, and terminating in a
round chamber. Others build a massive oven-shaped structure of clay on a
branch or other elevated site. Many of those that creep on trees nest in
holes in the wood. The marsh-frequenting kinds attach spherical or oval
domed nests to the reeds; and in some cases woven grass and clay are so
ingeniously combined that the structure, while light as a basket, is
perfectly impervious to the wet and practically indestructible. The most
curious nests, however, are the large stick structures on trees and
bushes, in the building and repairing of which the birds are in many
cases employed more or less constantly all the year round. These stick
nests vary greatly in form, size, and in other respects. Some have a
spiral passage-way leading from the entrance to the nest cavity, and the
cavity is in many cases only large enough to accommodate the bird; but
in the gigantic structure of Homorus gutturalis it is so large that, if
the upper half of the nest or dome were removed, a condor could
comfortably hatch her eggs and rear her young in it. This nest is
spherical. The allied Homorus lophotis builds a nest equally large, but