It is illegal to collect birds’ nests, feathers, or eggs without federal and state collecting permits.
Birds’ nests, hidden behind leafy curtains in the summer, often surprise us in the fall when they appear among the newly bare branches of trees. After the first snowfall, nests stand out as little snow-capped baskets perched on limbs or tucked away inside hedges and thickets. Although the birds that built them are probably far away, the size and shape, materials, and placement of nests can often give us clues about their identity. Birds build their nests without any prior instruction, and yet each builds a nest that is characteristic of its species.
All birds are warm-blooded, and the eggs they lay must be incubated in order for the young to develop and eventually hatch. The rounded eggs need to be kept together and kept warm. Both eggs and the brooding parent need protection from predators. A nest keeps the young safely together in one place where the parent can tend them.
The designs of bird nests are related to the habits and habitat of each species. Some birds simply lay their eggs on bare ground or a rock ledge. Others build simple nests on the ground, like the killdeer, which makes a shallow scrape in the loose gravel, or the ruffed grouse, which makes a shallow leafy nest on the forest floor. The downy young of these birds are precocial, able to run and hunt for food within hours of hatching, and so spend little time in the nest.
Other birds build more elaborate nests. Many of these have altricial young that are helpless and must be fed and cared for by the parents until they have grown their flight feathers and learned how to fly. Some birds build platform nests. Doves build loosely woven platforms of twigs. Ospreys and eagles build huge platforms out of branches and sticks that last for many years. Grebes build floating platform nests in wetlands. Cavity nesters like woodpeckers excavate holes in dead trees for their nests, while chickadees find already hollow trees in which to nest. Kingfishers and bank swallows dig tunnels in sandy banks and build their nests deep inside the ground. Some of the most elaborate and carefully woven nests are cup nests, the bowl shaped nests that are built by songbirds. Cup nests may sit on a branch, fit into the crotch of a tree, or hang from a branch. The red-eyed vireo builds a pensile nest, attached by its rim to a forked twig. Orioles weave bag-like pendulous nests that swing in the breezes, suspended from the tips of twigs, like cradles in the treetops.
Some birds do not build nests or even tend their own eggs. Cowbirds lay their eggs in the nests of other birds. When the baby hatches, it will be fed by the foster parent birds, and often it will push the other nestlings out of the nest. Cuckoos usually build their own nests, but occasionally leave their eggs in others’ nests, especially those of other cuckoos.
The location of a nest is critical to its success and is predictable for each species. Phoebes choose a spot under the eaves of a barn or house and often under a bridge, giving them the nickname “bridge birds.” House finches are apt to build nests in wreaths or hanging planters, which can be inconvenient for the homeowner. Goldfinches fasten their thistledown-lined cup nests within the upright crotch of a tree or shrub, and brown creepers hide their tiny nests behind the loose bark of a standing snag.
The materials used in nest construction give us clues about the nest builder. Orioles weave their hanging nests out of fibers stripped from the dead stalks of last year’s milkweed plants. Red-wing blackbirds build their nests out of sedges, rushes, and grasses, using milkweed fibers to bind them to cattails. Robins line their nests with mud that the female molds to the shape of her body like a potter smoothing out a bowl. Red-eyed vireos decorate their nests with curls of birch bark or paper from hornets’ nests. The ruby-throated hummingbird shingles its nest with bits of greenish-gray lichen. Chimney swifts break off twigs with their feet while on the wing and build delicate shelf-like nests using their sticky saliva for glue. Their Asian cousins, the swiftlets, build nests entirely with their bubbly saliva – a delicacy collected for birds’ nest soup.
Some birds include surprising items in their nests. The great-crested flycatcher usually places a snake skin in its cavity nest but may instead include a strip of plastic. Many species may use colorful yarn, string, or twine found during nest building. House wren nests usually include a variety of natural materials such as hair, wool, spider egg-cases, strips of bark, moss, and feathers, but some have been found to contain hairpins, nails, tacks, staples, hooks, and rusted pieces of wire!
An obvious choice for a soft lining that is warm and insulating is, of course, feathers. In some birds, like mallard ducks and great horned owls, the female will pull feathers from her own breast and use them to line her nest. The expression “feathering one’s nest,” meaning to enrich oneself, probably comes instead from songbirds like swallows and house finches that collect other birds’ feathers for lining their nests.
The process of building nests and rearing young can have many variations. In many songbird species, the female builds the nest alone. The bluebird female gathers nest material while the male stands guard on a fencepost or fights off competitors like tree swallows, which may attempt to usurp the nest cavity. With other species, such as in some swallows and waxwings, male and female work together. In the house wren, the male claims and defends several nest cavities, building a basic nest in each. The female inspects and selects one of these for her use or rejects them all and starts anew. Nest building generally takes a few days to a week. After that, females will usually lay an egg each day until the clutch is complete and then begin incubating. In this way, all the eggs will be ready to hatch at the same time.
The nests of birds, tucked away in nooks and crannies, serve to cradle and conceal both eggs and young. They are the visible results of complex innate behaviors that are critically important to the birds’ success in raising young. Comparing nests from different species of birds allows us to notice similarities in form and function as well as differences in location, material, and design.
Dunning, Joan. Secrets of the Nest. Boston: Houghton Mifflin, 1994.
Ehrich, Paul R., David S. Dobkin, and Darryl Wheye. The Birder’s Handbook: A Field Guide to the Natural History of North American Birds. New York: Simon and Schuster, 1988.
Harrison, Hal H. A Field Guide to Birds’ Nests. Peterson Field Guide Series. Boston: Houghton Mifflin, 1975.
Stokes, Donald W. and Lillian Q. Stokes. A Guide to Bird Behavior, vol. I-III. Boston: Little, Brown, 1983.
Cornell Laboratory of Ornithology website: www.birds.cornell.edu/AllAboutBirds/BirdGuide.