Bird nest

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For animal nests in general, see Nest. For the stadium referred to as "The Bird Nest", see Beijing National Stadium.

Deep cup nest of the Great Reed-warbler

A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term is popular in reference 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, the Village Weaver or the Red-browed Pardalote—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, or a mud dome with an entrance tunnel. Some species of cave swiftlets of the genus Collocalia make their nests entirely from their saliva, which dries and hardens to form a bracket on the cave wall into which the birds lay their eggs. The smallest bird nests are those of some hummingbirds, tiny cups which can be a mere 2 cm (less than one inch) across and 2–3 cm (about one inch) high.^[1] At the other extreme, some nest mounds built by the Dusky Scrubfowl measure more than 11 m (34 ft) in diameter and stand nearly 5 m (15 ft) tall.^[2] Although nests are primarily used for breeding they may also be reused in the non-breeding season for roosting and some species build special dormitory nests or roost nests (or winter-nest) that are used only for roosting.^[3]
Nests are built each year in most species but some birds refurbish their old nests. The large eyries (or aeries) of some eagles are platform nests that have been used and refurbished for several years.
In yet another extreme, brood parasites have evolved to manipulate and use host individuals either of the same or different species to raise the young of the brood-parasite, which relieves the parasitic parent from the building of nests and the investment of rearing young.
In most species, the female does all or most of the nest construction, though the male often helps.^[4] In some polygynous species, however, the male may do most or all of the nest building. The nest may also form a part of their courtship display such as in bowerbirds and weaver birds. The ability to choose and maintain good nest sites and build high quality nests may be selected for by females in these species. In some species the young from previous broods may also act as helpers for the adults.

Contents [hide] 1 Nest types 1.1 Scrape 1.2 Mound 1.3 Burrow 1.4 Cavity 1.5 Cup 1.6 Saucer or plate 1.7 Platform 1.8 Pendant 1.9 Sphere 2 Nest protection and sanitation 3 Colonial nesting 4 In human culture 5 References 5.1 Notes 5.2 Cited texts 6 External links

[edit] Nest types

Thick-billed Murres lay their single eggs directly onto rock ledges.

Not every bird species builds or uses a nest. Some auks, for instance—including Common Murre, Thick-billed Murre and Razorbill—lay their eggs directly onto the narrow rocky ledges they use as breeding sites.^[5] The eggs of these species are dramatically pointed at one end, so that they roll in a circle when disturbed. This is critical for the survival of the developing eggs, as there are no nests to keep them from rolling off the side of the cliff. Presumably because of the vulnerability of their unprotected eggs, parent birds of these auk species rarely leave them unattended.^[6]
King and Emperor Penguins also do not build nests; instead, they tuck their eggs and chicks between their feet and folds of skin on their lower bellies. They are thus able to move about while incubating, though in practice only the Emperor Penguin regularly does so. Emperor Penguins breed during the harshest months of the Antarctic winter, and their mobility allows them to form huge huddled masses which help them to withstand the extremely high winds and low temperatures of the season. Without the ability to share body heat (temperatures in the center of tight groups can be as much as 10C above the ambient air temperature), the penguins would expend far more energy trying to stay warm, and breeding attempts would probably fail.^[7]
Some crevice-nesting species, including Ashy Storm-petrel, Pigeon Guillemot, Eurasian Eagle-Owl and Hume's Tawny Owl, lay their eggs in the relative shelter of a crevice in the rocks or a gap between boulders, but provide no additional nest material.^[8][9] Potoos lay their single egg directly atop a broken stump, or into a shallow depression on a branch—typically where an upward-pointing branch died and fell off, leaving a small scar or knot-hole.^[10] Brood parasites, such as the New World cowbirds, the honeyguides, and many of the Old World and Australasian cuckoos, lay their eggs in the active nests of other species.^[11][12][13]