Birds build nests for the laying and incubating eggs. However, some species such as the weaver bird use their nests as elaborate display designed to attract potential mates. Various bird species have different types of nests made from an assortment of materials. To provide maximum protection for their young ones, birds cushion their nests using soft plant fibers, feathers, and other soft materials. Most of these nests have some degree of elasticity to accommodate the chicks as they grow and providing shade to protect the eggs and chicks from weather. When building their nests, birds seek to camouflage them with their surroundings or create them in secluded areas away from predators. Among most species, the female builds the nest with little or no assistance from the males. The architectural design of nests is often ingrained in the genetics of a a given species, as birds of similar species create the same nests whether or not in captivity.
Sphere nests are round and almost enclosed with a small opening often on the side which prevents rain water from entering. The structure of the nest keeps it relatively safe from predators by camouflaging with the environment. The American dipper, marsh wren, ovenbird, meadowlarks, and winter wren all construct sphere nests. These birds place their nests in low areas either close to the ground or on the ground, increasing the risk of predation.
Larger bird species such as egrets, osprey, the great blue eagle, the white stork, raptors and large wading birds make platform nests. The nests are typically built using larger twigs or sticks layered into a flat or shallow nest in sizes similar to those of the birds. The nests are either placed on the ground or in trees, often being built upon in each breeding season, to increase their size. Such nests sometimes weaken the branches of trees on which they are placed especially in areas prone to strong winds and storms.
Pendant nests are named for their appearance of interwoven sacks dangling from trees. Flexible materials like grass and plant fibers are interwoven to form the nest and are neatly attached to twigs or branches for strength. The entrance often faces downwards giving the bird protection from predators and weather elements. Species with pendant nests include weaverbirds, sunbirds, orioles, caciques and oropendolas.
Bird species such as the Atlantic puffin, the burrowing owl, the great hornbill, barbets, the crab plover, shearwaters, the kingfisher and kiwi, nest in burrows abandoned by other burrowing animals or bird. Various birds use different burrowing styles, often by using their beaks or feet and sometimes by flying at the nest. Some nests are dug horizontally into vertical cliffs, with the length varying depending on the species. The burrowing parakeet makes nests of up to ten feet long. Other ground-nesting species such as the puffbirds build their nests on the flat or gently sloping ground. The nest-interior may be lined with feathers or vegetation or left bare. Some birds burrow into tree trunks, such as the buff-breasted paradise-kingfisher. For security, burrow-nesting species live in colonies.
5. Saucer or plate
The saucer or plate-shaped nest differ from the cup-shaped nest by the depth, as they are deeper and less spread out. Saucer-shaped nests are common in wetlands. Saucer nests are not as thick as cup nests, which means that eggs are often left visible. Birds who build saucer nests include chimney swifts and mourning doves.
Cavity-nesting birds typically build their nests in anywhere from dead wood, tree trunks, cacti, gaps in houses and telephone poles. The cavities are either dug by the birds themselves, exist naturally, or are abandoned by other species. Woodpeckers, hornbills, trogons, bluebirds, some kingfishers, some owls, some ducks, the house sparrow, and chickadees are examples of cavity-nesting birds. These birds are in constant fear of predation by animals such as snakes. As a security measure, some smear mud or foul-smelling insects around the entrance or extending the chamber of the nest. The inner chamber is either left bare or is lined with soft, warm materials. The woodpecker’s nest is made on the underside of the branch to prevent flooding and reduce predation.
Mound nests are built from an accumulation of nesting materials such as twigs, vegetation, soil and branches in a cone or bell shape. These materials provide heat as they decompose which in turn warms and incubates the eggs. Temperature regulation techniques used by mound-nesting birds include opening them in the morning to allow warmth in or to release excess heat. The height of mound nests helps keep eggs away from ground temperatures. Males typically build these nests with some assistance from the females. The birds repair the piles for reuse in successive breeding seasons. Flamingos, the horned coot, the Adelie penguin, and the Malleefowl construct mound nests.
The cup-shaped nest is commonly built by species such as barn swallows, ruby-throated hummingbirds, yellow warblers, American robins and species of the passerines. The nest is typically placed on ledges, tree forks and along tree branches. Cup nests have a smooth hemispherical interior made from soft materials such as grasses and lined with feathers. The materials have to be flexible enough to be moulded. Nests are made stronger through the use of saliva and twigs. Density, thickness, mass, altitude, and depth of the nest influence the insulation and warmth of the nest.
The scrape nest is a simple one built mainly by ground-breeding birds such as the ostrich, most ducks, shorebirds, falcons, the sand grouse, quail, and pheasants. The nest is a shallow depression dug into the ground that is then often layered with soft vegetative matter, feathers or shell fragments (depending on the atmospheric and ground temperatures). This works to insulate the eggs while also preventing them from rolling off. However, the depth varies depending on the location of the birds. Birds in the Arctic and cooler regions build deeper nests to protect the eggs and young ones from cold winds. Since the eggs are relatively open to predators, the birds create display attractions to distract predators.