Birds build a wide variety of nests that can provide clues about the species that built them. While nests share common features like a bowl-shaped platform to hold eggs, the size, shape, materials, and location of nests can help identify the bird. Expert ornithologists can often identify a bird species just by the appearance and placement of an empty nest. For amateur bird watchers, observing a nest while occupied and seeing the adult birds around it are the best ways to determine what type of bird it belongs to.
What are the common features of bird nests?
While nests vary dramatically between species, they share some common features that enable them to serve the purpose of incubating eggs and sheltering young chicks. Most nests are built as a cup or bowl shape, with a indent to hold the eggs securely. The walls of the nest provide insulation to help keep the eggs and chicks warm. Nests are sturdy enough to withstand wind and support the weight of adult birds without collapsing. And nests are built in locations that help conceal and protect the vulnerable eggs and chicks from predators and harsh weather.
Beyond these basics, nests show incredible diversity in size, shape, materials used, location, and construction based on the needs of each species. Nest building is an innate behavior shaped by evolution to meet the unique needs of that particular species. The height, stability, insulation, camouflage, and attachment method of nests can point to the specific bird that built it.
Where do birds build nests?
Birds build nests in a variety of locations, both natural and manmade. Some of the most common natural nest sites include:
- Tree branches – Small cups built on branches in the canopy.
- Tree cavities – Nests built inside holes or rotted out trunks.
- Shrubs and vines – Woven nests built in dense vegetation.
- Cliffs – Nests on rocky ledges, often only accessible from flight.
- Ground – Nests built directly on the ground, hidden in vegetation.
- Burrows – Nest chambers excavated into dirt banks, often in colonies.
- Caves – Sheltered nests built on cave floors and walls.
- Nests parasitized – Nest built on top of another species’ nest.
In terms of manmade sites, birds often build nests on human structures like:
- Buildings – On ledges, eaves, signs, light fixtures.
- Bridges – On beams underneath bridges especially.
- Barns – Inside barns or on farm equipment.
The location of a nest provides clues about the species. Cavity nests indicate woodpeckers, bluebirds, or owls. Cup nests set along a cliff edge suggest raptors or vultures. Ground nests point toward upland game birds, shorebirds, or grouse.
What materials do birds use to build nests?
Birds construct nests from a variety of natural and manmade materials. These different building materials help create nests adapted to the bird’s ecology and behavior.
Some natural materials commonly used include:
- Twigs – Used as structural framework for many cup and platform nests.
- Grasses – Woven to form nest walls and cups.
- Mud – Used on its own or to cement twigs together.
- Animal hair – Provides insulative lining for nests.
- Feathers – Soft lining for more durable nests.
- Moss – Used for padding and moisture absorption.
- Spider silk – Used to anchor and reinforce nests.
- Snakeskin – Thought to deter predators.
- Seaweed – Binds coastal nests like those of alcids.
Birds will also readily scavenge manmade materials such as:
- String, yarn, thread – Used to weave cup nests.
- Paper, tissue – Makes soft nest lining.
- Plastic, cellophane – Often incorporated accidentally.
- Dryer lint – Excellent soft, cottony lining.
The materials a nest is constructed from offers clues about the species. Small twigs indicate songbirds. Mud points to swallows or swifts. Seaweed reveals seabirds. Tightly woven grasses suggest blackbirds or orioles. The materials present depend on what is available to the bird.
What are some common bird nest shapes and forms?
The overall form and structure of bird nests can vary dramatically between species while still serving the same purpose. Some of the most common nest designs include:
- Platform nests – Simple flat mats, like those of owls and hawks.
- Cup nests – Intricate twig cups woven together, used by many songbirds.
- Pendant nests – Suspended from tree branches, seen in orioles.
- Sphere nests – Globular woven nests with side entrance used by weaverbirds.
- Scrape nests – Shallow dirt depressions made by shorebirds and grouse.
- Burrow nests – Chambers and tunnels excavated into banks, common in puffins.
- Cavity nests – Nests built in existing tree hollows and holes.
- Floating nests – Buoyant masses of vegetation anchored in marshes.
- No nests – Some megapodes and maleo bury their eggs.
The overall form of the nest can indicate specific groups of birds. Cup and pendant nests imply songbirds. Platform nests suggest raptors, pigeons, or doves. Cavities indicate chickadees, owls, or woodpeckers. Scrapes signals shorebirds and gamebirds. Knowing the most common nest types helps narrow the possibilities.
How does nest size indicate bird species?
The size of a nest provides straightforward clues about what sized bird built it. Large birds build large nests, while small birds build tiny nests. Some typical sizes include:
- Hummingbird nests – Tiny, often as small as a thimble.
- Songbird nests – Range from 1-5 inches across.
- Hawk, crow, magpie nests – Can be up to 3 feet wide.
- Eagle, heron, osprey nests – Reach sizes of 4-6 feet across.
- Ostrich nests – Can be up to 8 feet wide.
Nest size sets reasonable expectations about the bird species. For example, finding a 5-inch nest would rule out both hummingbirds and eagles. Pay attention to whether the nest seems proportionate to ledges or branches around it, which offers scale cues.
What clues does nest placement give?
Where a bird chooses to locate its nest often follows patterns by species. Pay attention to nest height and placement for clues:
- Ground nests – Quail, grouse, plovers, ovenbirds.
- Shrub and vine nests – Cardinals, thrashers, cuckoos.
- Tree canopy nests – Warblers, tanagers, orioles.
- Tree trunk and cavity nests – Woodpeckers, nuthatches, owls.
- Building ledge nests – Phoebes, swifts, swallows.
- Pond edge and marshes – Grebes, coots, herons.
- Cliff ledges – Eagles, falcons, swifts.
Notice if nests are positioned out of reach from the ground, which may indicate tree-climbing species. Watch for nests built to blend into surroundings, like Killdeer scrapes that resemble rocks. Cliff locations mark colonial seabirds. Knowing where species nest traditionally helps pinpoint the likely builder.
What clues do nesting materials give?
Pay attention to the materials a nest is constructed from, which birds selectively build with based on availability. Some clues include:
- Mud nests – Swallows and swifts.
- Stick nests – Hawks, crows, robins.
- Grass and weed nests – Blackbirds, grackles.
- Twig and lichen nests – Mourning doves.
- Feather lined nests – Finches, hummingbirds.
- Trash lined nests – Crows, jays, sparrows.
Note interesting outliers too, like the snake skins in Yellow-billed Cuckoo nests or paper in Tree Swallow nests. Pay attention to how materials are woven since tighter weaving often indicates specific species. Knowing preferred materials will help point to the species.
What clues can the nest structure give?
Beyond materials, the overall structure and architecture of nests can provide hints about the bird species. Look for these structural clues:
- Extremely compact and knitted – Ovenbird, orioles.
- Delicate but sturdy walls – Warblers, vireos.
- Thick mud retort neck – Barn swallow.
- Roofed with side entrance – Cactus and rock wrens.
- Messy accumulation – Eagles, ospreys, herons.
- Hard packed clay – Swifts and swallows.
Pay attention to details like entrance shape and orientation, funnel length, interior chamber depth, and overall sturdiness. Structure aligns strongly with species groups like weaverbirds, seabirds, and raptors.
What are the best ways to identify nest builders?
While empty nests provide clues about their origins, the best way to definitively identify the owners is to directly observe birds at the nest. Try these tactics:
- Watch nests from a distance to see adults visiting.
- Note if you see pairs or solitary birds around the nest.
- Observe the bird’s bill shape, size, and coloration.
- Identify any distinctive field marks of visiting adults.
- Watch to see if adults are feeding nestlings.
- Listen for vocalizations of adults and young.
- Notice when fledglings eventually leave the nest.
With close observation and patience, seeing the comings and goings of adults and young makes positive identification straightforward in most cases. This avoids mistaken assumptions based only on the empty nest.
What are some examples of distinctive bird nests?
Some examples of unique nests that offer quick identification of their owners include:
- Pendulum nests of Baltimore Orioles
- Woven pouches on branches built by Yellow Warblers
- Mud oven-like nests on cliffs belong to Bank Swallows.
- Delicate moss baskets lined with feathers signal Hummingbirds.
- Bulky stick nests high on utility poles are Ospreys.
- Pit nests dug into sandy banks mark the Bank Swallow.
- Mat nests of sticks on the ground indicate Mourning Doves.
With experience, birders can learn to identify the origins of different nests at a glance. Unique structures, materials, locations, and sizes make many distinctive enough for solid guesses.
Conclusion
A bird’s nest reveals many behavioral and ecological clues about its builder. While constructed for the practical purpose of incubating eggs and sheltering young, nests also reflect the evolutionary pressures and innate preferences of each species. With careful observation of materials, architecture, placement, and contents, informed conclusions about nest owners become possible in many cases. While direct observation of the adults is ideal, nests provide helpful context and pointers for identification.
Bird nests showcase not just the diversity of avian species, but the innate artistry and architectural skills inherent in all birds. Appreciating the variety and complexity of their creations opens a window into the lives of birds and the constraints they overcome to successfully raise their young. Observing nesting behavior continues to captivate and inspire those eager to understand the natural world.