<P> The simplest nest construction is the scrape, which is merely a shallow depression in soil or vegetation . 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 . These materials may help to camouflage the eggs or may provide some level of insulation; they may also help to keep the eggs in place, and prevent them from sinking into muddy or sandy soil if the nest is accidentally flooded . 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 . </P> <P> 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 . Brooding adults also tend to be well camouflaged, and may be difficult to flush from the nest . Most ground - nesting species have well - developed distraction displays, which are used to draw (or drive) potential predators from the area around the nest . Most species with this type of nest have precocial young, which quickly leave the nest upon hatching . </P> <P> 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 . Studies have shown that an egg within a scrape nest loses heat 9% more slowly than an egg placed on the ground beside the nest; in such a nest lined with natural vegetation, heat loss is reduced by an additional 25% . The insulating factor of nest lining is apparently so critical to egg survival that some species, including Kentish plovers, will restore experimentally altered levels of insulation to their pre-adjustment levels (adding or subtracting material as necessary) within 24 hours . </P> <P> 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 . Others, including some shorebirds, cast shade with their bodies as they stand over their eggs . Some shorebirds also soak their breast feathers with water and then sit on the eggs, providing moisture to enable evaporative cooling . Parent birds keep from overheating themselves by gular panting while they are incubating, frequently exchanging incubation duties, and standing in water when they are not incubating . </P>

It is characteristic of many birds to build nests. this is an example of