“These adepts in bird-nest architecture have talents of the most varied sort. There are diggers, who scoop out a hollow in the sand; miners, who excavate a little cell to which a long and narrow passage gives access; carpenters, who bore into the trunk of a worm-eaten tree; masons, who work with mortar made of earth tempered with saliva; basket-makers, who weave together small twigs and fine roots; tailors, who with a filament of bark for thread and the beak for needle sew a few leaves together into a cornet for holding the mattress on which the young brood will rest; workers in felt, who make a fabric of down, hair, or cotton, that rivals our own similar products; and builders of fortresses, who protect their nest with an impenetrable thicket as a rampart. “The goldfinch, that pretty little red-headed bird which feeds on the seeds of thistles, builds a wonderfully wrought nest in the fork of some flexible branch. The outside is made of moss and the silky down of thistle-seeds and dandelions, while the inside, artistically rounded, is lined with a thick cushion of horse-hair, wool, and feathers. “The chaffinch builds its nest in nearly the same way, but, more mistrustful than the goldfinch, it covers the outside of its abode with a layer of gray lichen which, merging with the lichen growing naturally on the branch, serves to baffle the scrutiny of the bird-nest hunter. “The window-swallow makes its nest in the corners of windows, under the eaves of roofs, and in the shelter of cornices. Its building material is fine earth, chiefly that left in little piles after its digestion by earth-worms in fields and gardens. The swallow fetches it, a beakful at a time, moistens it with a little viscous saliva to make it stick together, and deposits it in courses, shaping the structure into a sort of hemispherical bowl fastened to the wall and having a narrow mouth at the top to allow the bird to squeeze through. Bits of straw embedded in this masonry of earth serve to give it greater solidity. Finally, the inside is upholstered with a quantity of fine feathers. “The chimney-swallow chooses a similar situation for its nest and uses the same building-materials, but the nest itself takes a different form. Instead of a hemispherical structure entered by a very small opening, it builds a cup-shaped nest, of no great depth and wide-open at the top. “Swallows like to live together in large numbers, so that their nests are sometimes found touching one another in colonies of several hundreds under the same cornice. Each pair recognizes unerringly its own belongings and respects scrupulously the property of others, in return for like respect paid to its own. There is among them a deep sense of solidarity, and they render mutual aid with no less intelligence than zeal.