The purpose of a bird nest is to hold the eggs of developing chicks. It protects the bird’s eggs from the elements, provides camouflage from predators, and gives fledging chicks a place to develop before they are independent. The type of nest used depends on the species.
Cup Nest
Robins construct the most common type of nest, called a cup nest. Generally, birds who make cup nests begin with a platform of twigs and grasses, including rootlets, dead grass, mosses, and occasionally man-made materials. These are held together with a layer of mud, then lined with finer material, such as cattail fluff, spiderwebs, fur, and hair.
Robins may install their nests in numerous locations, usually in trees or shrubs, but they are sometimes placed on the ground, in thickets, or even on a porch or gate. They are built in the fork between branches or beneath heavy foliage, with the outside diameter between 8-20 cm, taking 2-6 days to finish. Males gather nesting materials while females construct the nest, and the pair remains monogamous at least through the breeding season. Nests can be reused or rebuilt, with birds returning to the same nest site, but a new nest is often used for each brood.
Ruby-throated Hummingbirds, among the smallest of birds, also build cup nests, but they are much smaller than the robin’s nest. The nest is built near the tip or downward sloping part of a branch, taking 6-10 days, and measuring 4-5 cm wide.
The female hummingbird uses white plant down, bark shreds, and feathers for the outer layer, bound together with spider silk or the webbing from cocoons. The nest is often decorated with lichen, aiding in its camouflage, and can be reused, though not always by the original bird. Polygynous Ruby-throated Hummingbirds form no pair bonds, and males and females keep separate territories. Males can be highly territorial, defending nests with aggressive displays and vocalizations.
In addition to the robin’s cup nest, there are many other types of bird nests, variable in design and construction, some of which are listed here.
Weaving Nest
Birds create weaving nests by intertwining fibers using knots, loops, and hitches. The Red-winged Blackbird builds their nest near the ground near marshes, wetlands, and meadows, with the initial platform placed in between cattail stems. The outer structure is made from a platform and mud walls; inside they are woven together with fine grass and vegetation, then plastered together with more mud. The nest takes 3-6 days to make and is about 12 cm wide.
Males are polygynous, defending a territory with multiple females. Males often help to care for nestlings, primarily with the first female mated. The Red-winged Blackbird is very territorial, and people should watch out for the birds when near their nests to avoid being divebombed! The nests are known to be a host for Brown-headed Cowbirds’ brood parasitism.
Hanging Nests
Also called pensile nests, hanging nests are a form of cup nest that are suspended by the rim from a tree. Their design ranges from neatly woven, hanging cups, to enclosed pendulous structures.
Baltimore Orioles make hanging nests, placing them high up in cottonwoods or sycamores within deciduous woodlands and in residential areas. They consist of a deep woven pouch attached to thin, drooping branches or suspended by a small fork in a tree.
Males bring nesting material while females build the nest, using thin twigs and leaves, string, yarn, or bark strips for the outer wall, poking the material randomly to create knots. A middle layer of springy material is then lined with soft materials such as plant cotton, fine vegetation, and hair. The very sturdy nest measures about 9-21 cm in diameter, can take from one week to a month to build. The Baltimore Oriole builds a new nest for each brood, reusing the material from an older nest. The pair will return to the same tree if their breeding was successful.
Cavity Nest
Cavity nests can occur naturally in an existing hole in a live or dead tree or made by excavating an empty space within a living or a dead tree, log, or pole. Some species are excavators, while others, called cavity adopters, occupy already made cavities. Obligatory secondary cavity nesters rely on the nests excavated by other species to rear their young. Cavity nests are more secure than cup nests, having higher fledgling rates than other nest designs.
The Red-bellied Woodpecker is an excavator, drumming into the side of a tree, dead log, or a wooden pole in a variety of woodlands, as well as suburban neighborhoods and parks. The nest’s height varies, with the opening about 6 cm in diameter, and is lined with woodchips. The Red-bellied Woodpecker returns to the same nest tree but will excavate a new cavity directly below the old one.
The Eastern Screech Owl is a secondary cavity nester, reusing nests made by Red-bellied Woodpeckers. They may also find naturally occurring, deep tree cavities with a wide floor. The Eastern Screech Owls are permanent residents, forming life-long pair bonds, and nesting away from larger owls.
Black-capped Chickadees also nest in a variety of woodlands, parks, and suburban areas. They excavate cavities in softer trees, such as birch and aspen, or use the already made cavities from a variety of species. Black-capped Chickadees form a solitary and territorial monogamous pair that stays together for several breeding seasons.
Cavity nesters will sometimes use nest boxes, which are human-made enclosures. Other nest box users include bluebirds, wrens, and Purple Martins, which populate towering, multi-unit nest houses.
Scrape Nests
A surprising nest configuration is the scrape nest, which is essentially a small indentation, hole, or divot dug into open ground in sand, dirt, or gravel. They are sometimes lined with soft material. Many shorebirds and species like Wild Turkeys build scrape nests.
The Killdeer is a type of plover who scrapes a 7-9 cm wide nest on lawns, golf courses, athletic fields, and even in parking lots, lining it with sticks, shells, or other softer material. Being in the open leaves the nest vulnerable to predation, but the Killdeer has developed an interesting strategy for protection. If a predator comes too close, the Killdeer will pretend it has a wounded wing, hobbling away from the nest to lure invaders away by following the seemingly injured bird.
Mud Nest
This form of cup nest is primarily made from mud and dirt. Mud nests are found on the sides of vertical structures, both human-made and on cliff sides.
The Barn Swallow builds mud nests on rafters, ledges, and beneath the rooftop of buildings. The male and female both build the nest, collecting mud or dirt and mixing it with grass to form pellets. They first make a small shelf, then build up the walls, lining the nest with grass and feathers. When the pair reuses a nest, they will remove the contents and remake the mud rim. This species previously built nests in the cavities of trees and caves, but they are now well adapted to human development, having gotten the name Barn Swallow for making nests on barns. See their nests propped on the rafters on the sides of our Visitor Center’s roof.
Stick Nest
A stick nest is often large, placed on the tops of cliffs, but usually built on the top of a tall tree. It is constructed of larger sticks, then woven together with finer materials.
The Bald Eagle is a prime example of a stick nest builder, using a tall tree with a good view of the surroundings. They build it within a territory containing ample food resources near bodies of water. Males bring the materials to build the nest and females build it. It is made of sticks woven together with grass, moss, and cornstalks and lined with lichen, fine woody material, and a inner layer of downy feathers. It takes up to three months to build the nest, and Bald Eagles build two to three nests within a territory, inspecting the nests each year and choosing one to reuse. Eagles create the largest nests of the raptors, reaching up to 9 feet wide and weighing up to three tons.
When visiting the Center to view nests or observing them in your neighborhood or other natural area, it is important to respect nest etiquette. Avoid getting close to active nests so as not to disturb breeding birds. In sensitive species, disrupting a nest could cause nest failure. Migratory birds use a lot of energy to build nests, often having just travelled hundreds or thousands of miles to find a breeding territory, build a nest, and create a family. To get a close look at nests, approach them in winter when the birds are not using them.
With contributions from Michelle Allison, Laine Cotteleer, Zoe Finney, and Lindsay Focht.
