Talking about birds, we can’t separate them from their nests. Just like humans, birds have a home—a vital shelter. From the time the mother lays eggs to raising their young, the nest plays a crucial role.
Generally, each bird species has a different nest shape and location. Some birds build their nests in trees, while others nest on cliff ledges. The rest may nest on the ground, in underground burrows, tree holes, or even in buildings..
Although they nest in different places, almost all nests share essential parts, including anchors, an outer decorative layer, a structural layer, and a network. Nests are usually made from organic materials such as leaves, twigs, grass, or straw.
Like newlywed couples who want to have a home, bird pairs must also decide on the right location to build their nest. Some bird species, such as seagulls, choose the nest location together. However, in certain species, only the female selects the nest site, such as the Red-necked Phalarope (Phalaropus lobatus).
Once the nest location is determined and built, the female leaves the male to incubate the eggs. Conversely, in some species, the male selects the nest location, such as the House Sparrow (Passer domesticus) and the Eurasian Wren (Troglodytes troglodytes).
After selecting the location, the bird pair gathers materials and starts building the nest. The simplest method is tossing materials to the side of the developing nest. Some birds carefully place nesting materials to create a sturdier structure.
The most complex nests are built by tailorbirds, warblers, and sunbirds. These birds require special materials such as spider silk and bird feathers to weave or sew their nests. This intricate process demands high-level skills to weave materials together one by one until the nest takes shape.
Bird nests come in various models, although their basic shapes include bowl, dome, tubular dome, or plate. Nests built on the ground are usually in the form of beds, scrapes, or mounds, while those underground are typically burrows or holes.
Bowl Nests
This is the most common nest type and is widely recognized as the typical bird nest. It can be distinguished by having both an interior and exterior. Although more challenging to build, bowl nests provide maximum protection for eggs and young birds. They can be constructed in various places but are usually found in trees. The simplest positioning is by wedging them between tree branches. Some are attached and tied to tree trunks.
Enclosed Nests
This type is essentially an extended bowl nest. Enclosed nests have deeper walls with a roof and an entrance hole. Although no scientific theory has proven it, dome or enclosed nests appear to provide better protection for eggs and chicks compared to bowl nests.
Hanging Nests
Hanging nests, particularly woven ones, are among the most architecturally impressive bird homes. Built by hundreds of bird species, these nests are beautiful and require significant skill to construct.
These nests typically hang from branch tips, leaves, or between two tree twigs. Some are round with a single entrance hole, elongated, or resemble a test tube.
Regardless of their shape, almost all birds weave them from grass. The weaving process involves moving from one side to the other, threading strands of grass through the nest wall openings, and pulling them through to the other side.
Birds that sew their nests this way include species in the Zosteropidae family, such as the Japanese White-eye (Zosterops japonicus), the Mountain Tailorbird (Phyllergates cucullatus), and the Javan Prinia (Prinia familiaris).
Cavity Nests
Nesting in cavities is one of the best strategies compared to open nesting. This method is commonly used by birds in hazardous habitats or those with many predators.
Surveys show that the survival rate of eggs laid in open nests is only 50%, whereas those in cavity nests reach 70%.
Commonly known birds that nest in cliffside cavities include the Common Kingfisher (Alcedo atthis) and the Javan Kingfisher (Halcyon cyanoventris). These birds nest in holes in cliffs or riverbanks. Some dig their own nests, while others use abandoned nests from other birds.
Many bird species nest in tree holes, cacti, or even termite mounds. However, very few birds create their own holes in trees, such as the powerful woodpeckers. Most birds prefer to use existing tree holes, such as the Great Tit (Parus major) and the Javan Myna (Acridotheres javanicus). Others modify tree holes into nests, as seen in various parrot species like cockatoos.
A pair of Sumba cockatoos in their nest. (Foto: Anna Reuleaux)
Among cavity nest builders, hornbills are the champions. Nearly all of these large birds make their nests in tree cavities. This is no easy task for a bird as large as a hornbill, which can measure over one meter from beak to tail.
For instance, the Great Hornbill (Buceros bicornis), due to its massive size, only nests in cavities with a diameter of one to two meters, located at a height of 20-45 meters. In its native habitat, such large trees are becoming increasingly rare, hindering this species’ reproduction.
Incubator Nests
The strangest nests belong to mound-builders like megapodes and maleos. The Maleo (Macrocephalon maleo), a member of the Megapodiidae family (megapodes = large feet), has the most complex nesting habits. During breeding season, maleo pairs leave their forest feeding grounds to find sandy areas for laying eggs, often near hot springs or geothermal heat sources.
This process begins months before the breeding season. The male maleo prepares a nesting mound by scraping the soil to create a half-meter-deep hole, then covering it with leaves. The result is a five-meter-diameter mound standing one meter tall.
In this sand mound, the female digs a hole to lay her eggs. She then buries them in the sand and leaves them to incubate naturally until they hatch.
The Tanimbar Scrubfowl (Megapodius tenimberensis) builds its incubator nests near beaches and mangrove forests. Their cone-shaped mounds consist of wet soil or white sand mixed with decaying, wet leaves. These mounds can reach three meters in height and five meters in diameter.
Mud Nests
Birds don’t only nest in holes and twig bowls—some build mud nests, like flamingos. The Greater Flamingo (Phoenicopterus roseus) constructs its nests from piled mud and droppings in the middle of African soda lakes. Their nests typically form shallow mounds with a depression in the center.