Birds build nests to lay their eggs in and raise their young. Nests come in an incredible diversity of shapes, sizes and materials. Different species of birds build different types of nests depending on their needs and the materials available. The most fundamental purpose of a bird’s nest is to provide a safe place to lay eggs, keep them warm, and protect the chicks after they hatch. Beyond those basic functions, nests can also provide shelter from weather and predators. Understanding what various bird’s nests are constructed from provides insight into avian biology, behavior and ecology.
What Materials Do Birds Use to Build Nests?
Birds construct their nests from a variety of natural materials including:
- Twigs
- Grass
- Moss
- Mud
- Plant fibers
- Spider silk
- Feathers
- Hair
- Fur
The specific composition of a given nest depends on the materials available in the local habitat. The behavior and natural history of the species in question also plays a role. Some birds demonstrate incredible ingenuity, flexibility and adaptability in the materials they incorporate into nest building.
Twigs and Small Branches
Many birds construct the basic framework of their nests from small twigs and branches. These give the nest structure and allow it to take shape. Twigs form the fundamental nest material for many perching birds including corvids (crows, jays, magpies), thrushes, finches, sparrows, wrens and more.
Birds snap twigs off of trees and shrubs and weave them together into a nest. Some species are highly selective, insisting on particular sizes and shapes of twigs. The male and female often work together to build the nest, with one bird collecting materials and the other doing assembly.
Grass and Other Herbaceous Plants
Grasses, reeds, vines and other non-woody plants also get woven into bird’s nests. Grasses help provide a soft lining to the interior of twig frameworks. Longer flexible grass species can be used to tightly bind twiggy nest materials together. Dried native grasses are a primary nest component for many open country and wetland species.
Certain birds like weaverbirds and orioles are capable of tightly stitching together long grass blades into amazingly intricate hanging nest pouch structures. Other clever grass-working birds include the tailorbirds of Asia. Even hummingbirds incorporate soft plant down and fibers into their tiny thimble-sized nests.
Mosses and Lichens
In addition to vascular plants, some birds collect and use mosses, lichens and algae to construct and line their nests. Soft mosses help regulate nest moisture and temperature. Lichens gathered from tree bark also make a fine natural nest lining.
Various hummingbirds, swifts and even eagles incorporate moss into their nest architecture. The record probably goes to the Long-tailed Tit which constructs an elaborate domed moss nest reinforced with spiders webs and thousands of feathers.
Mud
Mud and clay provide excellent nest building materials for various species of swallows, swifts and martins. These aerial insectivores build mud nests in the form of retort-shaped structures stuck to vertical cliff faces and artificial structures.
Mud-daubers, a type of wasp, build similar mud nest conduits in which they lay their eggs. But swallow nest architecture is much more advanced allowing for a long breeding season with multiple clutches.
Both males and females participate in mud collection and nest construction. They ferry beakfuls of wet mud from nearby ponds and puddles back to the nest site thousands of times to complete construction. Mud nests require continual maintenance through the breeding season but can persist for many years.
Plant Fibers, Hair and Fur
For most bird species, the ideal nest contains a soft internal lining in addition to the basic structural framework. This helps cushion eggs and chicks and provides insulation. So birds often supplement twigs and grasses with softer stuff.
Cottonwood seeds, milkweed fibers, shredded bark, fine roots and other plant material provide natural nest lining. Feathers and down plucked from the parent birds’ breasts during breeding season also line many nests.
Hair and fur from other animals gets collected opportunistically. Birds decorate their nests with bits of yak fur snagged from bushes, tufts of buffalo fluff, clumps of horse hair and fibers from goat hair. Some urban birds even incorporate synthetic materials like string and fabric.
Spider Silk
Spider silk provides a valuable elastic and adhesive material. Some birds have mastered the technique of harvesting silk from spider webs. They carefully gather strands and weave them into the nest structure.
The most accomplished spider silk nest architects include the orioles. These colorful black and orange birds artfully stitch together nest pouches suspended from branches. Orioles use up to 70 feet of silk along with grass and fibers to build these intricate hanging baskets.
Hummingbirds also rely on spider silk to expand and reinforce their tiny cups. The fluffy, stretchy silk helps accommodate growing chicks in the nest.
Unique Nests Constructed by Particular Species
Beyond the materials used, the overall form and architecture of bird’s nests vary tremendously. Different bird clades have evolved specialized nest building behaviors tailored to their biology and natural history. Here are some examples of unique nests:
Tailorbird Nests
The aptly named tailorbirds of Asia are masters of nest construction. They carefully stitch together leaves using spider silk, plant fibers or even manmade threads. The leaves are pulled together to make a cozy protective capsule. Nests get built in thorny bushes, dense vines or suspended from branches.
Weaverbird Nests
Africa’s weaverbirds build perhaps the most impressive hanging nests. There are several dozen species of weavers, and the males construct intricate nests to attract females. Nest come in many forms like rounded chambers, long tubes or pendulous baskets. The most elaborate structures have separately-accessed nurseries built off of the main nest chamber.
Megapodes Mounds
Megapodes are a family of birds that build enormous nest mounds rather than conventional cup-shaped nests. Various species construct mounds from soil, sand, leaves, twigs and vegetation reaching heights of 15 feet tall and 30 feet across. The birds bury their eggs inside the decomposing organic matter which incubates them through geothermal heat.
Grebe Floating Mats
Grebes are water birds that actually build floating nest mats on the surface of lakes and ponds. The foundations are made of piled up aquatic vegetation which rots and becomes waterlogged. This allows grebe parents to simply roll their eggs into the center of the mat. The soggy mass provides cover while floating buoyantly.
Osprey Stick Towers
Ospreys construct huge stick nests atop trees, channel markers, cell phone towers and other elevated structures. The male and female carry sticks hundreds or thousands of times to build up a tower which can grow to 6 feet tall and 3 feet wide. The nest interior is softer but the imposing exterior helps protect the chicks.
Flamingo Mud Mounds
Like their relatives the grebes, flamingos build mound nests right in the shallow water of alkaline lakes. Both sexes gather mud with their beaks, sculpting it up into a conical pedestal 1-2 feet tall. The mound creates a raised platform to hold a shallow nest depression.
Eagle & Hawk Stick Nests
Many large raptor species erect substantial stick nests called eyries in trees or cliffs. The sturdy nests can grow to be 6 feet across and 3 feet thick, accumulating sticks and branches over many seasons. Bald eagles, golden eagles, several hawk species and other raptors use these nests year after year.
Kingfisher Burrows
Rather than construct an above-ground nest, kingfishers dig burrows into vertical dirt banks. Both males and females chip away soil with their long sharp beaks. The tunnel ends in a wider chamber suitable for a nest. Burrowing offers kingfishers natural temperature insulation. The nest chamber ranges from 1-8 feet deep.
Woodpecker Cavities
Woodpeckers chisel out their own nest cavities by hammering beak holes into dead trees. They hollow out a hole just large enough for their bodies. The interior of the cavity gets lined with wood chips. Strong muscles and skull adaptations protect the brain from the forces of chiseling.
How Do Birds Build Nests?
Constructing a complex nest structure requires a specific set of avian behaviors and adaptations. Here’s a look at how birds physically build nests:
Beak Manipulation
A bird’s beak allows for dextrous manipulation and shaping of nest materials. Harder beaks work like forceps to prune and tweak twigs into place. Scoop-shaped beaks ferry and tamp down softer lining materials. In some cases mates will pass materials back and forth to each other.
Feet Grasping
The feet also assist nest construction in most species. Grasping feet act like another pair of hands to hold and arrange materials. Longer toes allow for more dexterous manipulation. Weaving fibers together is accomplished by holding with the beak while pulling strands taut using the feet.
Body Twisting
Birds contort their bodies into odd positions while building nests. They twist to thread new materials into the cups, rims and sides of the nest. Able to pivot their heads nearly upside down, birds can reach the undersides and interiors of nests during construction.
Packing down
Birds will periodically tamp down the nest contents. Hopping inside the nest, they compress materials with their feet, breast and body. This firms up and tightens the structure while creating a soft depression to hold eggs. The tail may also be used like a shovel to corral nest materials.
Shaping the Interior
The interior of the nest requires special attention. After the framework is built, most birds line the inner bowl very deliberately. Softer materials get added and formed into a cup-shaped hollow using the beak, feet and breast.
Weaving and Stitching
More meticulous nest architects actually weave and stitch plant fibers or spider silk together. This requires a specialized technique of crisscrossing strands and fibers, then pulling them taut. Some birds dexterously knot materials using only their beaks and feet.
Mud Application
Mud nest specialists like swiftlets and swallows have evolved unique muddy beak “trowels”. Their beaks allow for scooping up soft wet mud and plastering it in place on vertical surfaces or nest structures. The mud then hardens to durable concrete.
Why Do Different Bird Species Build Different Nests?
The incredible diversity of avian nest structures reflects adaptations to specific lifestyles, habitats and behaviors:
Body Size
Smaller birds like hummingbirds build tiny nests with fine materials. Larger birds like eagles construct huge sturdy stick platforms. Nest size correlates with the size of adult birds and their chicks. Bigger nests provide more protective space.
Climate Adaptations
Birds in cold climates tend to build compact, thick-walled cup nests that insulate eggs and chicks. Some even create domed nests with narrow openings. In tropical regions nests tend to be more open and ventilated.
Weather Protection
Nests can be tailored to shield inhabitants from rain, wind and sun. Thick nest walls and suspended enclosed pouches help buffer the elements. Positioning nests in crevices or placing them below overhangs also provides cover.
Predator Avoidance
Spiny twigs, tough tightly woven materials and deep cavity nests help protect against predators. Placing nests over or in water hinders terrestrial predators. Sharp cliff and tree nests are inaccessible to many animals.
Habitat Materials
Birds exploit habitat-specific materials. Shorebirds use shells and pebbles near water. Cavity nesters need trees. Urban birds use scavenged trash and yard items. The availability of materials shapes each species’ nest design.
Nest Support
Some nests get built atop a substrate while others hang freely. Tree canopies support twig nests. Vegetation mats float nests over water. Cavities are carved into wood. Mud gets plastered onto walls or cliffs. Nest design revolves around anchoring.
How Do Birds Know How to Build Nests?
Birds possess an innate drive for nest construction coded into their biology and instincts. Like other animals, birds also have sophisticated cognitive capabilities that facilitate complex nest building:
Maternal Instruction
Nesting skills are not completely innate. Many young birds observe their mothers build nests and gain experience assisting with construction. This cultural transmission from generation to generation helps refine techniques.
Trial and Error Learning
First-time nest builders start out clumsy but improve with practice. Making mistakes and then compensating teaches birds how to construct more durable and practical nests.
Mating Display
More elaborate nests like woven pendulums or mounds evolve partly through sexual selection. Flashier nests help males show off and attract mates. Females choose males with superior nests denoting fitness.
Adaptability
Birds are extraordinarily adaptive when it comes to choosing materials and nest sites. This behavioral flexibility allows them to exploit diverse habitats and conditions for nest building.
Reasoning & Planning
There is evidence that birds plan their nest construction using cognitive skills like foresight, reasoning and problem solving. Great grey owl pairs, for example, appear to estimate future brood size when provisioning nest materials.
Conclusion
Nest building is an essential part of reproduction for most bird species. The diversity of avian nest structures provides a fascinating look into evolution and life history. Nests are constructed from the available plant, mineral and animal materials within a habitat. Architecture ranges from simple scrapes to complex woven pendulums. Nest construction behaviors are influenced by climate, predators, mating systems and parental care. Research continues to uncover new insight into the ornithological wonders of avian nest building.