Edible bird's nests, also known as swallow nests, are bird nests created from solidified saliva by edible-nest swiftlets, Indian swiftlets and other swiftlets of the genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia, which are harvested for human consumption.
Dried swiftlet nests ready for cooking
A bowl of bird's nest soup
Natural birds' nests, Ko Rangnok ('Bird's Nest Island'), Thailand
Nesting house for swiftlets, Ban Laem District, Phetchaburi Province, Thailand
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the elaborately woven hanging nest of the Montezuma oropendola or the village weaver—that is too restrictive a definition. For some species, a nest is simply a shallow depression made in sand; for others, it is the knot-hole left by a broken branch, a burrow dug into the ground, a chamber drilled into a tree, an enormous rotting pile of vegetation and earth, a shelf made of dried saliva or a mud dome with an entrance tunnel. The smallest bird nests are those of some hummingbirds, tiny cups which can be a mere 2 cm (0.8 in) across and 2–3 cm (0.8–1.2 in) high. At the other extreme, some nest mounds built by the dusky scrubfowl measure more than 11 m (36 ft) in diameter and stand nearly 5 m (16 ft) tall. The study of birds' nests is known as caliology.
Deep cup nest of the great reed-warbler
Some nest linings, such as the shell fragments in this Charadrius plover scrape, may help to prevent the eggs from sinking into muddy or sandy soil.
Other nest linings, like the lichen in this American golden-plover scrape, may provide some level of insulation for the eggs, or may help to camouflage them.
The huge mound nest of the malleefowl acts like a compost heap, warming and incubating the eggs as it rots around them.