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. 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.
King penguins 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 centre 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. 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.
The simplest nest construction is the scrape , which is merely a shallow depression in soil or vegetation. Eggs and young in scrape nests, and the adults that brood them, are more exposed to predators and the elements than those in more sheltered nests; they are on the ground and typically in the open, with little to hide them.
The eggs of most ground-nesting birds including those that use scrape nests are cryptically coloured to help camouflage them when the adult is not covering them; the actual colour generally corresponds to the substrate on which they are laid. Most ground-nesting species have well-developed distraction displays , which are used to draw or drive potential predators from the area around the nest.
In cool climates such as in the high Arctic or at high elevations , the depth of a scrape nest can be critical to both the survival of developing eggs and the fitness of the parent bird incubating them. The scrape must be deep enough that eggs are protected from the convective cooling caused by cold winds, but shallow enough that they and the parent bird are not too exposed to the cooling influences of ground temperatures, particularly where the permafrost layer rises to mere centimeters below the nest.
In warm climates, such as deserts and salt flats , heat rather than cold can kill the developing embryos.
In such places, scrapes are shallower and tend to be lined with non-vegetative material including shells, feathers, sticks and soil ,  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.
Some shorebirds also soak their breast feathers with water and then sit on the eggs, providing moisture to enable evaporative cooling. The technique used to construct a scrape nest varies slightly depending on the species. Beach-nesting terns, for instance, fashion their nests by rocking their bodies on the sand in the place they have chosen to site their nest,  while skimmers build their scrapes with their feet, kicking sand backwards while resting on their bellies and turning slowly in circles.
Burying eggs as a form of incubation reaches its zenith with the Australasian megapodes. Several megapode species construct enormous mound nests made of soil, branches, sticks, twigs and leaves, and lay their eggs within the rotting mass. The heat generated by these mounds, which are in effect giant compost heaps , warms and incubates the eggs. In most mound-building species, males do most or all of the nest construction and maintenance. 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.
This process can take five to seven hours a day for more than a month. While mounds are typically reused for multiple breeding seasons, new material must be added each year in order to generate the appropriate amount of heat.
A female will begin to lay eggs in the nest only when the mound's temperature has reached an optimal level. 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.
During hot summer months, the malleefowl opens its nest mound only in the cool early morning hours, allowing excess heat to escape before recovering the mound completely. Flamingos make a different type of mound nest. 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. The total combined weight of the mound's stones may approach 1. Once the mound has been completed, a sizable platform of aquatic vegetation is constructed on top.
The entire structure is typically reused for many years. Soil plays a different role in the burrow nest; here, the eggs and young—and in most cases the incubating parent bird—are sheltered under the earth. Most burrow-nesting birds excavate their own burrows, but some use those excavated by other species and are known as secondary nesters; burrowing owls , for example, sometimes use the burrows of prairie dogs , ground squirrels , badgers or tortoises ,  China's endemic white-browed tits use the holes of ground-nesting rodents  and common kingfishers occasionally nest in rabbit burrows.
Most burrow nesting species dig a horizontal tunnel into a vertical or nearly vertical dirt cliff, with a chamber at the tunnel's end to house the eggs. Birds use a combination of their beaks and feet to excavate burrow nests. 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. The latter method is not without its dangers; there are reports of kingfishers being fatally injured in such attempts. Female paradise-kingfishers are known to use their long tails to clear the loose soil.
Some crepuscular petrels and prions are able to identify their own burrows within dense colonies by smell. Not all burrow-nesting species incubate their young directly. Some megapode species bury their eggs in sandy pits dug where sunlight, subterranean volcanic activity, or decaying tree roots will warm the eggs. Predation levels on some burrow-nesting species can be quite high; on Alaska 's Wooded Islands, for example, river otters munched their way through some 23 percent of the island's fork-tailed storm-petrel population during a single breeding season in The cavity nest is a chamber, typically in living or dead wood, but sometimes in the trunks of tree ferns  or large cacti , including saguaro.
Far more species—including parrots , tits , bluebirds , most hornbills , some kingfishers, some owls , some ducks and some flycatchers—use natural cavities, or those abandoned by species able to excavate them; they also sometimes usurp cavity nests from their excavating owners. Those species that excavate their own cavities are known as "primary cavity nesters", while those that use natural cavities or those excavated by other species are called "secondary cavity nesters".
Both primary and secondary cavity nesters can be enticed to use nest boxes also known as bird houses ; these mimic natural cavities, and can be critical to the survival of species in areas where natural cavities are lacking. Woodpeckers use their chisel-like bills to excavate their cavity nests, a process which takes, on average, about two weeks.
The endangered red-cockaded woodpecker is an exception; it takes far longer—up to two years—to excavate its nest cavity, and may reuse it for more than two decades. 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. The process may take several months, and a single pair may start several excavations before finding a tree or stump with wood of the right consistency.
Species which use natural cavities or old woodpecker nests sometimes line the cavity with soft material such as grass, moss, lichen, feathers or fur. Though a number of studies have attempted to determine whether secondary cavity nesters preferentially choose cavities with entrance holes facing certain directions, the results remain inconclusive. Cavity-dwelling species have to contend with the danger of predators accessing their nest, catching them and their young inside and unable to get out.
Red-cockaded woodpeckers peel bark around the entrance, and drill wells above and below the hole; since they nest in live trees, the resulting flow of resin forms a barrier that prevents snakes from reaching the nests.
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. The cup nest is smoothly hemispherical inside, with a deep depression to house the eggs. Most are made of pliable materials—including grasses —though a small number are made of mud or saliva.
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. Many swifts and some hummingbirds  use thick, quick-drying saliva to anchor their nests. The chimney swift starts by dabbing two globs of saliva onto the wall of a chimney or tree trunk. In flight, it breaks a small twig from a tree and presses it into the saliva, angling the twig downwards so that the central part of the nest is the lowest.
It continues adding globs of saliva and twigs until it has made a crescent-shaped cup. More recently, nest insulation has been found to be related to the mass of the incubating parent. Nest walls are constructed with an adequate quantity of nesting material so that the nest will be capable of supporting the contents of the nest.
Nest thickness, nest mass and nest dimensions therefore correlate with the mass of the adult bird. The saucer or plate nest, though superficially similar to a cup nest, has at most only a shallow depression to house the eggs. The platform nest is a large structure, often many times the size of the typically large bird which has built it. Depending on the species, these nests can be on the ground or elevated. In some cases, the nests grow large enough to cause structural damage to the tree itself, particularly during bad storms where the weight of the nest can cause additional stress on wind-tossed branches.
The pendant nest is an elongated sac woven of pliable materials such as grasses and plant fibers and suspended from a branch. Oropendolas , caciques , orioles , weavers and sunbirds are among the species that weave pendant nests. The sphere nest is a roundish structure; it is completely enclosed, except for a small opening which allows access.
Many species of bird conceal their nests to protect them from predators. Some species may choose nest sites that are inaccessible or build the nest so as to deter predators. Birds have also evolved nest sanitation measures to reduce the effects of parasites and pathogens on nestlings. Some aquatic species such as grebes are very careful when approaching and leaving the nest so as not to reveal the location.
Some species will use leaves to cover up the nest prior to leaving. Ground birds such as plovers may use broken wing or rodent run displays to distract predators from nests. Many species attack predators or apparent predators near their nests. Natural red cave nests are often found in limestone caves in a bird nest concession island in Thailand. Because the bird's nest is an animal product, it is subject to strict import restrictions in some countries, particularly with regard to H5N1 avian flu.
Import of nests into Australia is strictly prohibited unless imported with an official Customs and Quarantine import permit from the Australian Department of Agriculture. From Wikipedia, the free encyclopedia. Edible bird's nest Edible bird's nest. Retrieved 7 March Retrieved 20 August A few species of swift , the cave swifts , are renowned for building the saliva nests used to produce the unique texture of this soup.
Translating the Suiyuan Shidan. House of Bird's Nest. Retrieved 9 January Retrieved 20 January Computers and Electronics in Agriculture. Neural Computing and Applications. Expert Systems with Applications. Canadian Food Inspection Agency. Retrieved 29 July Fermented bean curd Five-spice powder XO sauce.
Chinese herb tea Dried shredded squid. Retrieved from " https: Chinese soups Cantonese cuisine Hong Kong cuisine Bird breeding. EngvarB from July Use dmy dates from July Articles containing Chinese-language text All articles with unsourced statements Articles with unsourced statements from September Articles with unsourced statements from August Articles with unsourced statements from September Commons category with page title different than on Wikidata.
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