What if birds forgot how to build nests?

A robin builds a cup of grass for its eggs. Many birds build nests.

What if all the birds forgot how? Where would they put their eggs?

Every spring, birds get busy carrying twigs, grass and moss to build nests. A nest is a cradle: a place to lay eggs, keep them safe, and raise the chicks that hatch.

What if every bird suddenly forgot how to build one? In this thought experiment, you will find out what nests do, discover the amazing range of nests birds make, and meet some birds that already lay their eggs without a nest at all.

Birds build nests of many kinds, from simple scrapes to woven domes and cavities. Nests protect eggs and young, and research links different designs to concealment from predators and to protection from harsh climates.

This thought experiment imagines all birds losing the ability to build. It draws on a 2026 global analysis of nest types and on species that already reproduce without a built nest, to ask what nests do and what the alternatives cost.

A nest keeps eggs safe. A roof can hide them from hungry animals.

A nest in a tree hole keeps eggs warm on cold nights and cool on hot days.

Nests protect eggs and chicks. In 2026, scientists in Taiwan and the United States looked at the nests of more than 7,400 kinds of birds. They found that nests with a roof, called domed nests, mainly help hide eggs and chicks from predators. Nests in tree holes and burrows mainly protect against harsh weather, because wood and soil keep the temperature steady.

Some nests do both. The sora, a marsh bird, weaves a roof of living cattails and sedges over its nest, which shelters the birds from the weather.

A team from Academia Sinica's Biodiversity Research Center and the University of Maryland (Global Ecology and Biogeography, June 2026) analyzed nest types in more than 7,400 species, about 74 percent of known birds. In passerines, domed nests were more common where predator diversity was higher, consistent with a role in concealment and blocking access. Cavity nests were more common in dry regions with large temperature swings, where tree trunks and soil insulate eggs and nestlings.

The authors note that artificial nest boxes often insulate less than natural cavities, which matters for conservation as climates change.

Without nests, eggs might roll away or get too cold.

Hungry animals might find them more easily. Baby birds would have no cozy home.

If every bird forgot how to build a nest, eggs would have to be laid on the bare ground, on branches or on rock. Without a cup to hold them, eggs might roll off. Without a roof or a hole, they might be easier for predators to spot, and harder to keep at the right temperature.

Chicks would have no soft, safe place to grow up. Birds might have to spend more time guarding and warming their eggs. Some might manage; many might struggle.

Losing nest-building would remove the concealment benefits of domed nests and the thermal buffering of cavities that the 2026 study links to predation and climate. Eggs on exposed surfaces might suffer higher predation and greater temperature stress, and parents might need to compensate with more attentive incubation and defense.

How severe this would be would vary by species: birds already adapted to nest-free laying would be little affected, while those relying on enclosed nests in harsh climates or predator-rich areas might fare worst. These are inferences, not predictions.

Birds make cups, platforms and holes. They use twigs, grass, hair and even spider silk!

Sociable weavers build one giant nest that hundreds of birds share.

Bird nests come in three main kinds: cups, platforms and cavities, or holes. Canada geese make cups on the ground, grebes build floating platforms, and wood ducks nest in tree holes. Cerulean warblers bind bark, grass and hair together with spiderwebs. A ruby-throated hummingbird's nest is only about 5 centimeters (2 inches) across, made of plant down held together with spider silk; its walls stay stretchy, so the nest grows with the chicks.

In Africa's Kalahari Desert, sparrow-sized sociable weavers build enormous shared nests like apartment buildings, housing weaver families by the hundreds. The nests stay cool in summer and warm in winter.

Summit Metro Parks naturalist Ben Mullaly describes three main nest types: platforms (grebes), cavities (wood ducks) and cups (Canada geese, on the ground). Materials range widely: cerulean warblers bind bark, grass and hair with spiderwebs, and ruby-throated hummingbirds hold thistle or dandelion down together with spider silk, camouflaging the outside with lichen; the pliable walls stretch as the chicks grow (Cornell Lab of Ornithology).

The most spectacular builders are sociable weavers of the Kalahari, whose communal nests house families by the hundreds. Robert Thomson (University of Cape Town) calls them ecosystem engineers: the nests stay cool in summer and warm in winter, other birds such as pygmy falcons occupy spare chambers, and the birds' droppings enrich the soil beneath the tree.

Some birds don't build nests! Murres lay one egg on a bare cliff ledge.

Emperor penguin dads hold the egg on their feet. Cuckoos lay eggs in other birds' nests.

Some birds already manage without building a nest. Common murres lay a single egg straight onto a cliff ledge above the sea; the egg is very pointed at one end. Killdeer just scratch a shallow dip in bare ground and lay their eggs there.

Emperor penguin fathers keep the egg off the ice by balancing it on their feet under a warm fold of feathered skin, for about two months, without eating. And female common cuckoos skip all the work: they lay their eggs in other birds' nests and let those birds raise their chicks.

All About Birds notes that common murres lay their single egg directly on a cliff ledge, sometimes arranging pebbles that become cemented by guano, and that the egg is very pointed at one end. Killdeer nests are shallow scrapes about 3 to 3.5 inches across; parents lure predators away with a broken-wing display.

Emperor penguin males incubate the egg on their feet under a brood pouch for about two months while fasting (National Geographic). Common cuckoos are brood parasites: a female lays 12 to 22 eggs a season, each in a different host's nest, removing one host egg each time (RSPB). Each species has replaced the nest with another solution.