[edit] Cup

Cup nest of a Common Blackbird

Cup nest of a Redwing, with newly hatched chicks

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. Many passerines and a few non-passerines, including some hummingbirds and some swifts, build this type of nest.
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.^[69][70] The lightweight material is strong and extremely flexible, allowing the nest to mold to the adult during incubation (reducing heat loss), then to stretch to accommodate the growing nestlings; as it is sticky, it also helps to bind the nest to the branch or leaf to which it is attached.^[70]

[edit] Saucer or plate

The saucer or plate nest, though superficially similar to a cup nest, has at most only a shallow depression to house the eggs.

[edit] Platform

The huge platform nest of the Osprey

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.^[71] In the case of raptor nests, or eyries (also spelt aerie), these are often used for many years, with new material added each breeding season. 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.

[edit] Pendant

Taveta Golden Weaver building pendant nest

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.

[edit] Sphere

The sphere nest is a roundish structure; it is completely enclosed, except for a small opening which allows access.

[edit] Nest protection and sanitation

Many species of bird conceal their nests to protect them from predators. Some species may choose nest sites that are inaccessible. Some may make specific modifications to keep predators at bay. Bird nests can also act as habitats for other inquiline species which may not affect the bird directly. 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.^[72]
Many species attack predators or apparent predators near their nests. Kingbirds attack other birds that come too close. In North America, Northern Mockingbirds, Blue Jays, and Arctic Terns can peck hard enough to draw blood.^[73] In Australia, a bird attacking a person near its nest is said to swoop the person. The Australian Magpie is particularly well-known for this behavior.^[74]
Nests can become home to many other organisms including parasites and pathogens.^[75] The excreta of the fledglings also pose a problem. In most passerines, the adults actively dispose the fecal sacs of young at a distance or consume them. This is believed to help prevent ground predators from detecting nests.^[76] Young birds of prey however usually void their excreta beyond the rims of their nests.^[77] Blowflies of the genus Protocalliphora have specialized to become obligate nest parasites with the maggots feeding on the blood of nestlings.^[78]
Some birds have been shown to choose aromatic green plant material for constructing nests that may have insecticidal properties,^[79][80] while others may use materials such as carnivore scat to repel smaller predators.^[81]

Nesting colony of Montezuma Oropendolas

Some birds use pieces of snake slough in their nests.^[82] It has been suggested that these may deter some nest predators such as squirrels.^[83]

[edit] Colonial nesting

Main article: Bird colony

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. Birds that nest colonially may benefit from increased protection against predation. They may also be able to better utilize food supplies, by following more successful foragers to their foraging sites.^[84]

[edit] In human culture

Many birds nest close to human habitations and some have been specially encouraged. Nesting White Storks have been protected and held in reverence in many cultures.^[85] Nest boxes are often used to encourage cavity nesting birds. The nesting of Peregrine Falcons on tall buildings has captured popular interest.^[86] Colonial breeders produce guano which is a valuable fertilizer. The saliva nests of Cave Swiftlets are used to make Bird's nest soup in parts of Southeast Asia.
Some species of birds are also considered nuisances when they nest in the proximity of human habitations. Feral pigeons are often unwelcome and sometimes also considered as a health risk.^[87]
The Beijing National Stadium, principal venue of the 2008 Summer Olympics, has been nicknamed "The Bird Nest" because of its architectural design, which its designers likened to a bird's woven nest.^[88]
In the Victorian era, naturalists often collected bird's eggs and their nests. The study of bird nests is called caliology.^[89]