and tree builders sometimes get upon the ground or into a tussock of
grass. The song-sparrow, which is a ground builder, has been known to
build in the knot-hole of a fence rail, and a chimney swallow once got
tired of soot and smoke, and fastened its nest on a rafter in a hay
barn. A friend tells me of a pair of barn swallows which, taking a
fanciful turn, saddled their nest in the loop of a rope that was
pendent from a peg in the peak, and liked it so well that they
repeated the experiment next year. I have known the social sparrow, or
"hair bird," to build under a shed, in a tuft of hay that hung down,
through the loose flooring, from the mow above. It usually contents
itself with a half a dozen stalks of dry grass and a few long hairs
from a cow's tail, loosely arranged on the branch of an apple-tree.
The rough-winged swallow builds in the wall and in old stone heaps,
and I have seen the robin build in similar localities. Others have
found its nest in old, abandoned wells. The house wren will build in
anything that has an accessible cavity, from an old boot to a
bombshell. A pair of them once persisted in building their nest in the
top of a certain pump-tree, getting in through the opening above the
handle. The pump being in daily use, the nest was destroyed more than
a score of times. This jealous little wretch has the wise forethought,
when the box in which he builds contains two compartments, to fill up
one of them, so as to avoid the risk of troublesome neighbors.

The less skilful builders sometimes depart from their usual habit, and
take up with the abandoned nest of some other species. The blue-jay
now and then lays in an old crow's-nest or cuckoo's-nest. The
crow-blackbird, seized with a fit of indolence, drops its eggs in the
cavity of a decayed branch. I heard of a cuckoo that dispossessed a
robin of its nest; of another that set a blue-jay adrift. Large, loose
structures, like the nests of the osprey and certain of the herons,