Why Birds Build Nests
No matter what style a bird uses, all nests serve the same purpose: to protect eggs and hatchlings. There are different ways nests do this, including:
Cushioning: Many nests are lined with soft plant fibers, animal fur, fine grasses, feathers, moss, and similar materials that provide cushioning for the eggs. This protects the eggs even when a brooding adult may be moving around on top of the nest. Most nests also have a degree of flexibility or elasticity to continue protecting growing hatchlings without breaking or collapsing. Shelter: Nests help shade and protect eggs and chicks from poor weather. Some birds do this by creating nests that include roofs or overhangs. More often, however, the nest is positioned in a sheltered location out of the wind and protected from the worst of the hot summer sun, stormy winds, or drenching rains. Camouflage: Eggs and chicks are exceptionally vulnerable, and most nests are constructed to help keep the birds and eggs hidden from predators. Birds may do this by building their nest in a hidden location or by using materials to help conceal the nest. Bits of bark, lichen, moss, or other materials are often used to decorate the outside of the nest as camouflage.
In some cases, nests also help attract mates, and some birds build especially elaborate nests or may start several nests in different locations to better appeal to a mate. Once the partnership is formed, the nest construction will be finished and the eggs laid.
Bird Nest Designs
Birds can create many different types of nests. While the same species will always create the same sort of nest structure, because birds can’t change their minds and invent new nest styles, there is great variety among nests types.
Cup: A simple cup-shaped nest is the most familiar, common nest type. The overall size, dimensions, and depth of the cup may differ, and some birds build distinct inner and outer cup layers. Cups are often positioned along tree branches or in tree forks or may be nestled on ledges or in any number of unique places.Birds That Build Cup Nests: Barn swallows, ruby-throated hummingbirds, yellow warblers, American robins, and many different passerines. Scrape: A basic scrape is a shallow depression on the ground without much nesting material, though it may have a light lining of down, grass, pebbles, weeds, or other debris. Scrapes are popular nest types for terrestrial birds or birds that prefer open habitats that lack abundant trees, such as shorebirds or tundra species.Birds That Build Scrape Nests: Common ostrich, killdeer, American avocet, Arctic tern, and many shorebirds. Burrow: A nesting burrow is dug into the ground and may be a shallow cave or could have a long tunnel leading to a nesting chamber. These nests are often excavated in soft material such as loose dirt banks or guano accumulation. The inner nesting chamber may be lined with some material or could be bare. Birds may excavate their burrows or may usurp suitable burrows from other animals.Birds That Nest in Burrows: Atlantic puffin, burrowing owl, great hornbill, barbets, kiwis, and many kingfishers. Mound: A mound nest is built on the ground but is a relatively large accumulation of nesting material in a tall cone or bell-shaped structure. The eggs may be nearly buried in the nest, which helps provide additional protection and insulation, or they can rest on top of the mound. The height and diameter of the nest mound will vary.Birds That Build Mound Nests: Horned coot, Adelie penguin, malleefowl, and most flamingo species. Cavity: Cavity-nesting birds are common and will either excavate their nesting cavities or use natural cavities in trees, snags, or cacti. Holes in telephone poles or even nestled in gaps in houses as well as birdhouses are also great options for cavity-nesting species. The interior cavity may be bare or could be lined with a variety of materials, and some birds may even build loose cups inside the cavity.Birds That Use Nest Cavities: Eastern bluebird, house sparrow, most woodpeckers, many parrots, tits, and chickadees. Platform: A platform nest is a relatively large, bulky structure often built of larger twigs or sticks. The surface is typically flat or may have a very shallow depression, but not enough to be considered a deliberate cup. Many birds reuse platform nests for many years, often adding material to the nest each year.Birds That Build Platform Nests: Bald eagle, osprey, great blue heron, white stork, and many other raptors and large wading birds. Pendant: Pendant nests are elaborately woven sacks that dangle from branches, giving birds in the nest great protection from predators. Some are not suspended very far from the branches while others may hang several feet below their attachment point. Birds enter the nest through an entrance on the side.Birds That Build Pendant Nests: Baltimore orioles, caciques, oropendolas, and most weaver bird species. Sphere: A sphere or dome nest is almost completely enclosed and provides great protection and camouflage. The trade-off, however, is that these nests are often on the ground or in low areas and may be more susceptible to predators. The nest entrance is typically on the side so it still protects from the rain.Birds That Build Sphere Nests: American dipper, marsh wren, winter wren, ovenbird, and different meadowlarks.
Birds Without Nests
While birds can be very creative architects, several bird species have no nests at all. Some species, such as the peregrine falcon, common murre, and emperor penguin, simply lay their eggs in the open or a relatively secluded spot without actually having a nest structure. Other birds, such as the brown-headed cowbird, are brood parasites that lay their eggs in other birds’ nests, abandoning their parental duties completely. Birds’ nests are amazing structures that come in a wide range of sizes and styles. Understanding more about why and how birds build nests gives birders even better insights into the amazing lives and reproductive habits of their favorite bird species.
