Bird nest

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.

[10] 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.

[11][12] 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.

[17] This nest type, which typically has a rim deep enough to keep the eggs from rolling away, is sometimes lined with bits of vegetation, small stones, shell fragments or feathers.

[19] Ostriches, most tinamous, many ducks, most shorebirds, most terns, some falcons, pheasants, quail, partridges, bustards and sandgrouse are among the species that build scrape nests.

In such places, scrapes are shallower and tend to be lined with non-vegetative material (including shells, feathers, sticks and soil),[25] which allows convective cooling to occur as air moves over the eggs.

Some species, such as the lesser nighthawk and the red-tailed tropicbird, help reduce the nest's temperature by placing it in partial or full shade.

[34] Marbled godwits stomp a grassy area flat with their feet, then lay their eggs, while other grass-nesting waders bend vegetation over their nests so as to avoid detection from above.

[35] Many female ducks, particularly in the northern latitudes, line their shallow scrape nests with down feathers plucked from their own breasts, as well as with small amounts of vegetation.

[36] Among scrape-nesting birds, the three-banded courser and Egyptian plover are unique in their habit of partially burying their eggs in the sand of their scrapes.

Several megapode species construct enormous mound nests made of soil, branches, sticks, twigs and leaves, and lay their eggs within the rotting mass.

[38] The size of some of these mounds can be truly staggering; several of the largest—which contain more than 100 cubic metres (130 cu yd) of material, and probably weigh more than 50 tons (45,000 kg)[38]—were initially thought to be Aboriginal middens.

Using his strong legs and feet, the male scrapes together material from the area around his chosen nest site, gradually building a conical or bell-shaped pile.

While mounds are typically reused for multiple breeding seasons, new material must be added each year to generate the appropriate amount of heat.

[40] Both the temperature and the moisture content of the mound are critical to the survival and development of the eggs, so both are carefully regulated for the entire length of the breeding season (which may last for as long as eight months), principally by the male.

This regular monitoring also keeps the mound's material from becoming compacted, which would inhibit oxygen diffusion to the eggs and make it more difficult for the chicks to emerge after hatching.

Using their beaks to pull material towards them,[44] they fashion a cone-shaped pile of mud between 15–46 cm (6–18 in) tall, with a small depression in the top to house their single egg.

[44] The base of the horned coot's enormous nest is a mound built of stones, gathered one at a time by the pair, using their beaks.

[50] Puffins, shearwaters, some megapodes, motmots, todies, most kingfishers, the crab plover, miners and leaftossers are among the species which use burrow nests.

[53] Some species, including the ground-nesting puffbirds, prefer flat or gently sloping land, digging their entrance tunnels into the ground at an angle.

The tunnel is started with the beak; the bird either probes at the ground to create a depression, or flies toward its chosen nest site on a cliff wall and hits it with its bill.

[61] There is some evidence that increased vulnerability may lead some burrow-nesting species to form colonies, or to nest closer to rival pairs in areas of high predation than they might otherwise do.

[62] The cavity nest is a chamber, typically in living or dead wood, but sometimes in the trunks of tree ferns[63] or large cacti, including saguaro.

The size and shape of the chamber depends on species, and the entrance hole is typically only as large as is needed to allow access for the adult birds.

While wood chips are removed during the excavation process, most species line the floor of the cavity with a fresh bed of them before laying their eggs.

Trogons excavate their nests by chewing cavities into very soft dead wood; some species make completely enclosed chambers (accessed by upward-slanting entrance tunnels), while others—like the extravagantly plumed resplendent quetzal—construct more open niches.

Most female hornbills seal themselves into their cavity nests, using a combination of mud (in some species brought by their mates), food remains and their own droppings to reduce the entrance hole to a narrow slit.

Small bird species in more than 20 passerine families, and a few non-passerines—including most hummingbirds, kinglets and crests in the genus Regulus, some tyrant flycatchers and several New World warblers—use considerable amounts of spider silk in the construction of their nests.

[102] Though most birds nest individually, some species—including seabirds, penguins, flamingos, many herons, gulls, terns, weaver, some corvids and some sparrows—gather together in sizeable colonies.

[103] In constructing nests, birds act as ecosystem engineers by providing a sheltered microclimate and concentrated food sources for invertebrates.

Deep cup nest of the great reed-warbler
Three eggs, bluish with black speckling, sit atop a layer of white mollusc shells pieces, surrounded by sandy ground and small bits of bluish stone.
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.
Female peregrine falcon nest-scraping on artificial ledge on Derby Cathedral . Both sexes contribute to the creation of a bare, shallow depression in soil or gravel.
Four beige eggs, heavily speckled with black, sit in a shallow depression lined with pale greenish-white lichen.
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.
A large pile of bare earth stands amidst pale tree trunks, bleached grass and fallen sticks.
The huge mound nest of the malleefowl acts like a compost heap, warming and incubating the eggs as it rots around them.
Two long-legged, long-necked pink birds stand atop cylindrical piles of mud, with water in the background.
The mound nests of flamingos, like these Chilean flamingos , help to protect their eggs from fluctuating water levels.
Like most burrow-nesting species, sand martins dig a horizontal tunnel into a vertical dirt cliff.
Increased vulnerability to predators may have led some burrow-nesting species, like the European bee-eater , to become colonial breeders.
"Secondary cavity nesters", like this cobalt-rumped parrotlet , use natural cavities or holes excavated by other species.
Only a relatively small number of species, including the woodpeckers, are capable of excavating their own cavity nests.
Like many small birds, the purple-crowned fairy uses considerable amounts of spider silk in its cup nest.
Cup nest of a common blackbird
A bed nest on a tree
A pair of long-tailed tits in the process of building a nest
Hanging bird nest
Many raptors, like the osprey , use the same huge platform nest for years, adding new material each season.
Some waterbirds, including the grebes , build floating platform nests.
Taveta golden weaver building pendent nest.
Nesting colony of Montezuma oropendolas
Two bird nest close to each other
Two expired bird nest.
Three long-legged, long-billed black and white birds stand on a huge pile of sticks atop an artificial platform on a pole.
A human-made nest platform in Poland built as a conservation measure and to prevent storks disrupting electricity supplies through nesting on pylons. Three young white storks are on the top of the nest and two Eurasian tree sparrows are perching on the side of the nest.
Artificial duck nest