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Most birds build some type of nest in order to lay their eggs and raise their young. The selection of the place where to locate the nest and its construction are aspects of fundamental importance in the reproduction of birds. It is in the nest where the eggs will be deposited, they will incubate and, after the birth of the young, the parents will care for and educate them until they are young adults. Therefore, guaranteeing the safety of the nest with respect to environmental threats and predators is decisive for the success of the reproductive process.
Not all birds build nests, and a particular case is the emperor penguin, which covers the only egg it produces and then the chick with a fold of its abdomen, and transports it on its legs to protect it from the Antarctic cold.
Built taking advantage of natural cracks or built in complex structures; Located on top of a tree, on platforms over the water or on the ground, the nests have very different characteristics. Erected by the joint work of the couple, which can sometimes have different roles, the birds build them with available materials, such as mud or branches, and line their interior with feathers or leaves to give comfort to the eggs and growing chicks. . Let’s see the main characteristics of the nests through the following classification.
scratched nest
The dug nest is the simplest type of nest a bird can build. Birds usually implant them in a shallow depression in the ground, sometimes adding stones, feathers, shells, or leaves to the edges of the depression. The womb nest shown below is an example of a scratch nest.
Eggs laid in dug nests are often camouflaged, as their location on the ground makes them highly vulnerable to predators. Birds that build digging nests tend to have precocious young, and are therefore capable of leaving the nest quickly after hatching. In addition to the womb, the rhea, seagulls, hawks, pheasants, quails, partridges, bustards and vultures, among many other species, build scratched nests.
hanging nests
Hanging nests are built by creating a structure suspended from a tree branch. The bird uses flexible materials such as grass, elongated leaves, or very thin branches. The first of the following two figures shows the African southern masked weaver bird beginning the construction of a hanging nest, where it can be seen how the bird weaves with elongated leaves the anchorage of the nest to a branch and the structure around which it will build the nest. nest, whose final shape can be seen in the second figure. The southern masked weaver can weave dozens of nests in three to four months.
nest in cavity
Cavity nests are holes in tree trunks, both live and dry, that birds use to lay eggs and raise chicks. There are also nests in holes in large cacti and vines.
Only a few species, such as woodpeckers, curucúes and barbudos, are capable of digging a cavity in a trunk to build their nest. These birds are classified as primary cavity nest builders. Woodpeckers take about two weeks to dig their nest, which is usually located under a branch to protect it from rain and predators, and is used for a single season. A special case is the red-crested woodpecker ( Leuconotopicus borealis) that takes up to two years to excavate its nest and uses it for two decades. Most cavity nesting birds use natural hollows or nests abandoned by other species. Parrots, owls and some ducks are some of the many species that nest in natural cavities or generated by other species. Birds that nest in holes are the most likely to breed in aviaries.
nest in burrow
Burrow nests are shelters excavated by birds in the ground using their beaks and feet. Most birds make their own burrow nests but some, like certain owl species, prefer to use nests made by other species or implant them in natural holes. Burrow nests are built by digging a tunnel in a gully or in the ground; These tunnels can be between fifty centimeters and one meter, and those built by the burrowing parakeet can measure up to three meters.
This type of nest is commonly used by seabirds, especially those that live in cold climates, as a burrow nest protects from both predators and the weather.
nest on platform
Platform nests are large, flat-based nests built in trees, on the ground, on top of vegetation, or even on rocks in shallow water. Many platform nests are reused year after year by the same birds, adding materials to the nest each time they use it. This constructive type can generate large nests. The osprey, herons, storks and many birds of prey build their nests on platforms.
mound nests
Like burrow nests, mound nests serve the dual purpose of protecting eggs from predators and keeping them comfortable in harsh climates. Mound nests are made of mud, twigs, sticks, and leaves. Similar to a compost pile, the nest heats up when organic material begins to decompose; the mass of organic matter in a mound nest rots and generates essential heat to incubate the chicks.
It is the males that build the mound nests in most cases, using their strong legs to stack materials. The female will only lay her eggs when the temperature inside the mound has reached an optimum level. During the incubation period, the male will continue to add material to the nest to maintain the correct size and temperature. Flamingos and some turkeys are examples of birds that build mound nests.
nest in bowl
Bowl-shaped nests are shaped as their name suggests, with a deep depression inside to protect the eggs and chicks. They are built with materials such as mud, grass and small branches, a combination that allows them to be shaped like a bowl. Some species also use spider web in the construction of the nest, since it is a light, resistant and very flexible material, which allows the nest to conform to the adult during incubation, thus reducing heat loss, and shrinking later to contain the chicks during their growth. Since it is a sticky material, it also helps anchor the nest to the branch or leaf it is attached to. Hummingbird nests are an example of a bowl nest, as shown in the presentation figure of the article.
Sources
Antimio Cruz. Through trial and error, birds build their nests. Budget Science , 2011.
