Nests in Trees: Which Animals Build Them and Why

Tree nests are constructed by a wide range of animals, including birds, squirrels, primates, social insects, and even some amphibians and mites. These structures serve as protective sites for eggs, young, and resting adults, and they vary enormously in form, material, and location depending on the builder's biology and environment. This article examines the major groups of arboreal nest builders, the adaptations that enable them to nest in trees, and the practical considerations for observing and managing tree-nesting species.

At a Glance: Major Tree-Nesting Animals and Their Nest Types

The table below summarizes the primary tree-nesting animal groups, their typical nest forms, and the tree features they commonly use. This information is useful for field identification, habitat assessment, and conservation planning.

Birds as Arboreal Nest Builders

Bird nests have long attracted human interest, both as beautiful creations and as important constructions. They are important constructions because avian parents use them to protect their developing eggs and young from the dangers presented by the elements and predators. Despite sharing these protective functions, bird nests can be remarkably structurally variable, being built from a wide diversity of materials and placed in all manner of locations. For example, male Australian brush turkeys scrape material into large nest mounds, woodpeckers excavate holes, storks build stacks, sparrows and swallows build cups of different materials, while weavers weave their famous hanging baskets. Nests might be built in bushes or holes in trees, dangle from a branch, or sit on the ground. They might be solitary and hidden, or conspicuous, together housing hundreds of families.

Cavity Nesters and Excavators

Woodpeckers are primary cavity excavators, meaning they create their own nesting holes in tree trunks. These cavities are later used by secondary cavity nesters such as European rollers, which nest mainly in holes in natural cliffs, cliffs of anthropogenic origin, and tree hollows. In the Stavropol Region, European rollers used tree hollows for 15.7 percent of their nests, with the majority placed in natural and anthropogenic cliff holes. Cavity nesting provides protection from predators and weather, but it requires trees of sufficient size and decay state to allow excavation.

Cup Nesters and Platform Builders

Sparrows and swallows build cup-shaped nests, though they use different materials. Storks construct large stick platforms, often in tall trees or on artificial structures. The structural diversity of bird nests reflects the different selective pressures each species faces, including predation risk, microclimate, and material availability.

Elaborate Pendent Nests as Structural Defenses

The pendent nests of some weaverbird and icterid species are among the most complex structures built by any animal. The precarious attachments and extended entrance tunnels characteristic of these nests are widely speculated to act as structural defenses against invasion by nest predators, particularly tree-climbing snakes. Phylogenetic comparative methods investigating the relationship between nest structure and developmental period length in weaverbirds and icterids found that more elaborate nests, particularly those with entrance tunnels, are associated with longer developmental periods in both families. This finding is robust to potentially confounding effects of body mass, phylogenetic relationships, nest location, and latitude. These results are consistent with the hypothesis that elaborate nest structures in birds can function as structural defenses, resulting in lower offspring mortality and slower development. Constructing complex, protective structures may buffer against environmental hazards, reducing extrinsic mortality and contributing to the evolution of slower life histories in diverse animal lineages.

Squirrels and Their Dreys

Tree squirrels build nests called dreys, which are spherical structures of leaves, twigs, and bark, typically placed in the fork of a branch high in the canopy. Dreys provide insulation from cold and rain, protection from predators, and a secure site for rearing young. Squirrels may maintain multiple dreys within their home range and move between them in response to weather, disturbance, or parasite load.

The construction of a drey begins with a platform of interwoven twigs, followed by a hollow interior lined with soft materials such as moss, grass, or fur. The outer shell is continuously repaired and expanded as the squirrel uses the nest. Dreys are most visible in deciduous trees after leaf fall, making late autumn and winter the best time for surveys.

Great Apes: Arboreal Nest Builders and Their Significance

Nest building is a great ape universal, and arboreal nesting in chimpanzees and bonobos suggests that the common ancestor of Pan and Homo also nested in trees. It has been proposed that arboreal nest-building remained the prevailing pattern until Homo erectus, a fully terrestrial biped, emerged. Nest building is a necessary skill and form of tool use that individuals learn and practice early in life.

Chimpanzee Nest Construction and Development

All great apes build nests. Nests in trees or on the ground provide apes with a safe and comfortable place to sleep and rest at night and during the day. Studies of wild immature chimpanzees at Ngogo, Kibale National Park, Uganda, evaluated the effects of age, sex, and maternal parity on the likelihood of infant nest building, as well as on the rates and durations with which infants built nests. Compared to the youngest infants of one year or less, older infants were more likely to build nests and built them at higher rates, consistent with hypotheses that nest building requires learning in early infancy and a threshold of physical development to manipulate tree branches. Female infants were more likely to build nests and built them more often than male infants, corroborating other developmental markers suggesting females attain functional independence at younger ages than males in some chimpanzee populations. Among infants who were seen to build nests at least once, rates and durations were similar regardless of age, sex, or maternal parity, indicating that there was little interindividual variation in nest building development once infants started practicing. The observed patterns of prior and subsequent behaviors to nest building suggested that infants older than four years built nests more functionally, for resting, than younger infants.

Tree Species Selection and Habitat Use

In the non-protected area of Diaguiri in southeastern Senegal, surveys of 43 kilometers of chimpanzee nesting habitats recorded 871 nests in gallery forest and woodland habitats. Diaguiri chimpanzees used at least 17 tree species for nest building, and 58.8 percent of nests were in only three tree species: Pterocarpus erinaceus, Anogeissus leiocarpus, and Diospyros mespiliformis. Nest decay rate was faster in gallery forests than in woodlands. These data are of great value for understanding habitat use by a Critically Endangered subspecies of savanna chimpanzee, for population density estimates of the species, and for conservation programs in this region and in savanna biomes.

Social Learning of Nest-Building Skills

Immature great apes learn how to build their nests over multiple years. Research on wild Sumatran orangutans using data on nest-building, nest practice, and nest peering behavior from 44 individuals collected over 17 years found that nest peering, but not being close to a nesting individual without peering, is associated with a significant increase in nest practice and is primarily directed at multi-step nest elements. Dependent immatures mostly peer at their mothers and use nest tree species in common with her, while independent immatures peer at a larger range of individuals and use nest tree species in common with them. These results suggest that orangutans acquire their nest-building skills through observational social learning, selective attention to know-how, and the transmission of know-what information.

Thermoregulatory Function of Nests

Nest building by great apes provides a context to examine whether behavioral adjustments reflect reactive responses to current conditions or proactive anticipation of conditions yet to come, because nests function both as sleeping platforms and thermoregulatory structures. Research on eastern chimpanzees recorded in situ measurements of temperature, humidity, wind speed, and rainfall at the time of nest construction and during the subsequent overnight period. Chimpanzees preferentially constructed nests in warmer, less windy microclimates, built thicker and deeper nests under cooler or wetter conditions, and selected taller trees with denser canopy cover prior to rainy nights. Models that incorporated overnight weather consistently outperformed those that incorporated weather variables at the time of nest construction, indicating that nesting decisions align more closely with overnight conditions than with conditions at the time of nest building. This outcome is consistent with the possibility that chimpanzees adjust nest-building behavior in relation to expected overnight thermal conditions, potentially using proximate cues, although it does not provide conclusive evidence of anticipatory decision-making.

Ground Nesting and the Tree-to-Ground Transition

Ground nesting in chimpanzees may inform on factors influencing the tree-to-ground sleep transition in the hominin lineage. Research at Seringbara in the Nimba Mountains, Guinea, used a novel genetic approach to examine ground nesting in unhabituated chimpanzees. Ground nesting was a male-biased behavior, and males constructed more elaborate night nests than simple day nests on the ground. The mate-guarding hypothesis was not supported, as ground and associated tree nests were built either by maternally related males or possibly by the same individuals. Ground nesting was widespread and likely habitual in two communities. These findings suggest that terrestrial nest building may have already occurred in arboreally adapted early hominins before the emergence of Homo erectus.

Social Insects That Build Arboreal Nests

Social insects are among the most prolific arboreal nest builders, constructing structures that can house thousands of individuals and persist for years.

Arboreal Ants and Nest Homeostasis

Arboreal ants occupy a thermally dynamic environment, yet the mechanisms integrating nest architecture and worker behavior to maintain colony homeostasis remain understudied. Research on Azteca chartifex spiriti, a Neotropical arboreal species that builds large polydomous nests suspended in trees, measured internal moisture and temperature gradients in the main nest, which houses most individuals, including the reproductive female, immatures, and numerous workers. The results show integrated thermoregulatory mechanisms that combine passive strategies, derived from nest architecture and moisture gradients from the suspension base to the lower extremity, with active strategies linked to foraging patterns and worker polymorphism. Internal temperature remained buffered relative to external fluctuations, and moisture was significantly higher at the nest's lower extremity. Worker size displayed a bimodal distribution during the day that shifted to a unimodal pattern at night, indicating behavioral adjustments to thermal and operational demands. These findings demonstrate that the interaction between physical structure and worker behavior maintains colony homeostasis, providing essential insights into how dominant canopy ants may cope with future climate change scenarios.

Termites and Their Arboreal Nests

Social insect colonies function as ecological units whose size directly shapes the abundance of associated organisms. Research on Constrictotermes cyphergaster sampled 60 arboreal nests across four localities in the Brazilian semiarid to investigate how the volume of this structure shapes termitophile abundance. Nest volume positively predicted the abundance of symbionts, with each additional liter increasing the expected count by 2.4 percent, generating an accumulation rate in abundance of nearly five-fold between small and large colonies. Volume did not predict the probability of a nest harboring no termitophiles, indicating that colony size modulates carrying capacity post-colonization instead of facilitating initial invasion. Abundance differed among species, with Termitocola silvestrii numerically outnumbering both Corotoca species, and varied across landscape, as urban areas harbored substantially fewer symbionts than rural sites. Despite the increase in absolute abundance of symbionts, the ratio of termitophiles per worker remained constant across the entire volume gradient, suggesting active population tracking, host tolerance, or passive chemical integration.

Invasive Hornets and Their Nesting Cycle

The yellow-legged hornet (Vespa velutina nigrithorax) is an invasive species established in the European Union since 2004. In Galicia in northwest Spain, around 28,000 nests are identified per year. When weather conditions are suitable, the queen starts the life cycle by building the embryo nest and laying the first eggs. This first stage of the colony is composed of the queen, a few small workers, and sometimes males, living in a fragile nest usually situated in a protected place. After this, the nest continues to develop to a larger size, which leaves the nest more exposed in places such as tree canopy. The period of decline begins in autumn with the appearance of breeding individuals and ends with the fecundation of new queens that will form the future colony in the next cycle. Embryo nests are mainly found in buildings in spring, while secondary nests are observed in vegetation in summer and autumn. The high reproduction rate of this species has led to its successful expansion into many regions, causing significant losses in agriculture and beekeeping and posing a risk for human health.

Other Arboreal Nest Builders

Tree Frogs

Phyllomedusa trinitatis is a tree frog found in Trinidad and Venezuela that has mostly been studied for its nest building and breeding behavior. Tree frogs in this genus construct leaf nests by folding leaves and gluing them with secretions, creating a moist chamber for egg deposition. These nests are typically positioned over water so that hatching tadpoles drop into the aquatic environment below. Tracking studies using thread bobbins and radio-telemetry in dense rainforest environments found that bobbins were cheaper and allowed visualization of the detailed path taken, including substrates used, but caused more bruising due to entanglement. The tracker weight rule of 10 percent of body weight was found to be too restrictive for this species, with trackers up to 15 percent of body weight used with no significant impacts on distances traveled. Frogs became lethargic when bearing trackers longer than two days, so tracking in the field was limited to one overnight period.

Mites Associated with Arboreal Nests

The mite genus Ulyxes is associated with a narrow range of nest types, being confined to arboreal nests, usually tree hollows, and on the parrot or mammal hosts that use them. This genus has a broad range of feeding behavior spanning intranasal parasitism, nidicolous parasitism, and at least one species is a nidicolous predator. Its host range is broad, with two species shown to cohabit with parrots while most remaining species associate with mammals. The strong contrast between male chelicerae of predatory and parasitic species has not been previously observed in such a compact dermanyssine genus, complicating previous attempts to recognize male mouthparts as reliable features marking higher-level natural groups.

Rodents and Arboreal Nests

The thicket rat Grammomys poensis is considered the main natural host of murine Plasmodium species in Central Africa. Field research in southeastern Gabon over 18 months involved trapping across twelve forest fragments using both Tomahawk traps and direct collection at nest. Despite intensive effort of 12,150 trap-nights and 1,380 nests inspected, only 20 adult Grammomys were captured, all by collection directly at nest, and none were infected with Plasmodium as determined by two sensitive nested-PCR assays. The absence of infection may reflect local extinction of Plasmodium lineages, limited vector exposure due to the absence of species feeding on arboreal rodents, or host resistance. This study demonstrates that arboreal rodent nests can be sampled directly, though capture success may be low even with substantial effort.

Practical Assessment of Tree-Nesting Species

For land managers, researchers, and farmers who encounter tree nests, a systematic assessment approach helps identify the builder and determine appropriate management actions.

Step 1: Identify the Nest Type

Examine the nest structure, materials, and location. Woven hanging baskets indicate weaverbirds. Leaf and twig balls in branch forks indicate squirrel dreys. Large platforms of bent and broken branches high in trees indicate great ape nests in appropriate geographic regions. Carton or paper structures on trunks or branches indicate social insects. Excavated holes in trunks indicate woodpeckers or other cavity nesters.

Step 2: Record Nest Dimensions and Position

Measure the nest diameter, height above ground, and distance from the trunk. Note the tree species and whether the nest is in a fork, on a branch, or suspended. Record the aspect and canopy cover. These measurements support population monitoring and habitat modeling.

Step 3: Assess Activity

Look for fresh material, recent droppings, vocalizations, or insect activity. For squirrel dreys, fresh leaf additions indicate active use. For bird nests, observe parental visits during the breeding season. For insect nests, worker traffic indicates activity.

Step 4: Document and Monitor

Maintain records of nest locations using GPS coordinates. Photograph each nest from consistent angles. Revisit nests at regular intervals to track construction, occupancy, and decay. For chimpanzee nests, decay rates vary by habitat, with faster decay in gallery forests than in woodlands, so monitoring intervals should account for local conditions.

Records and Measurements for Nest Monitoring

Consistent record keeping supports both research and management decisions. The following measurements are relevant across taxa:

For chimpanzee nest surveys, standardized methods developed for arid landscapes have been implemented during national surveys. Nest decay rates are poorly understood in savanna-woodland mosaic habitats, so local calibration is essential for accurate density estimates.

Common Failure Patterns in Nest Observation and Management

Several recurring problems affect those who study or manage tree-nesting species.

Misidentification of Nest Builders

Many nests are abandoned or reused by different species across seasons. A cavity excavated by a woodpecker may later house a roller or a squirrel. A drey may be occupied by a different squirrel individual or species. Confirm the current occupant before making management decisions.

Disturbance During Sensitive Periods

Approaching nests during egg laying, incubation, or early chick rearing can cause abandonment or increased predation. Limit observation frequency during these periods and maintain adequate distance. For tree frogs, trackers caused lethargy when worn longer than two days, so tracking was limited to one overnight period to minimize welfare impacts.

Invasive Species Overlooked in Early Stages

The yellow-legged hornet builds small embryo nests in spring that are easily overlooked. These nests are usually in protected places such as buildings, while secondary nests in tree canopies are more conspicuous. Early detection of embryo nests allows more effective control before colonies expand.

Incomplete Habitat Assessment

Nest surveys that focus only on one habitat type may miss important nesting areas. Chimpanzees in Senegal used both gallery forest and woodland habitats, with different nest decay rates in each. Surveys limited to one habitat will produce biased density estimates.

Welfare and Safety Considerations

Observing and managing tree nests requires attention to both animal welfare and human safety.

Animal Welfare

Minimize disturbance to nesting animals. For research involving tracking devices, pilot studies should assess welfare impacts before full deployment. The 10 percent body weight rule for trackers was too restrictive for tree frogs, but trackers up to 15 percent of body weight caused no significant impacts on distances traveled. However, frogs became lethargic when bearing trackers longer than two days, so tracking duration was limited.

Human Safety

Nests of social insects, particularly invasive hornets, pose direct risks to human health. The yellow-legged hornet causes significant losses in agriculture and beekeeping and is a risk for human health. Nests in tree canopies may require professional removal. Ground-based observers should maintain safe distances from active insect nests and use appropriate protective equipment.

Regulatory Context

Many tree-nesting species are protected by national and international regulations. Chimpanzees are a Critically Endangered subspecies in some regions, and their nests are indicators of habitat use for conservation programs. Invasive species such as the yellow-legged hornet may be subject to control requirements. Check local regulations before disturbing any nest.

Professional Escalation Criteria

Certain situations warrant consultation with specialists or regulatory authorities.

When to Consult a Wildlife Specialist

• Nests of great apes or other protected primates are found, particularly in regions where such species are rare or endangered
• Nests of threatened or endangered bird species are identified
• Active nests are found in trees scheduled for removal or pruning
• Unusual nest structures or materials are observed that cannot be identified

When to Contact Pest Management Professionals

• Active nests of yellow-legged hornets or other stinging insects are found near human activity areas
• Large arboreal ant or termite nests threaten structural integrity of buildings or infrastructure
• Repeated infestations occur despite control efforts

When to Report to Conservation Authorities

• Chimpanzee or other great ape nests are found in areas where the species was previously unknown
• Nest surveys reveal population changes that may indicate broader ecological shifts
• Evidence of illegal nest destruction or wildlife disturbance is observed

Limitations of Current Knowledge

Several gaps in understanding tree-nesting animals remain.

Nest Decay Rates

Variations in nest decay rates are poorly understood in savanna-woodland mosaic habitats. Decay rates affect population estimates derived from nest counts, so inaccurate decay assumptions produce biased density estimates. Local calibration studies are needed across habitat types.

Behavioral Flexibility

The extent to which nest-building decisions reflect anticipation of future conditions versus response to current conditions remains unclear. Chimpanzee nesting decisions align more closely with overnight conditions than with conditions at the time of nest building, but this does not provide conclusive evidence of anticipatory decision-making.

Climate Change Impacts

Climate-change-induced phenological mismatches have reduced food availability for migratory animals that breed in northern latitudes. Novel pathogens and parasites are spreading northwards, and nest or offspring predation has increased at many Arctic and northern temperate locations. Altered trophic interactions have decreased the reproductive success and survival of migratory animals. Changes in the benefits of migration need to be integrated into projections of population and ecosystem dynamics and targeted by innovative conservation actions.

Symbiont Ecology

The factors regulating termitophile populations within arboreal termite nests are not fully understood. Nest volume modulates carrying capacity post-colonization instead of facilitating initial invasion, but the mechanisms maintaining constant symbiont-to-worker ratios remain untested. Hypotheses include active population tracking, host tolerance, or passive chemical integration.

Frequently Asked Questions

What animals build nests in trees?

Birds, squirrels, great apes, social insects, tree frogs, and some mites build or use nests in trees. Birds construct woven baskets, cups, stick platforms, and excavated cavities. Squirrels build dreys of leaves and twigs. Chimpanzees and orangutans build sleeping platforms of bent branches. Arboreal ants, termites, and hornets construct carton or paper nests. Tree frogs fold leaves into chambers for eggs. Some mites live exclusively in arboreal nests of birds and mammals.

What animals build nests called dreys?

Tree squirrels build dreys, which are spherical nests of leaves, twigs, and bark placed in branch forks high in the canopy. Dreys provide insulation, protection from predators, and secure sites for rearing young. Squirrels may maintain multiple dreys within their home range and move between them in response to weather, disturbance, or parasite load.

Why do birds build such different types of nests?

Bird nests vary because different species face different selective pressures, including predation risk, microclimate, and material availability. Woodpeckers excavate holes for protection, storks build stick platforms for large broods, sparrows and swallows build cups from different materials, and weavers weave hanging baskets. Elaborate pendent nests with entrance tunnels are associated with longer developmental periods, suggesting they function as structural defenses against predators such as tree-climbing snakes.

How do chimpanzees learn to build nests?

Chimpanzees learn nest building through a combination of physical development and social learning. Infants begin practicing at an early age, with older infants building nests more often and more functionally. Female infants build nests more often than male infants in some populations. Observational social learning is important, as nest peering is associated with increased nest practice in orangutans, and immature apes use nest tree species in common with the individuals they peer at.

Do all great apes build nests?

Yes, nest building is a great ape universal. All great apes build nests, and arboreal nesting in chimpanzees and bonobos suggests that the common ancestor of Pan and Homo also nested in trees. Nests in trees or on the ground provide apes with a safe and comfortable place to sleep and rest at night and during the day.

What tree species do arboreal nest builders prefer?

Tree species preferences vary by region and builder. Chimpanzees in Senegal used at least 17 tree species for nest building, with 58.8 percent of nests in only three species: Pterocarpus erinaceus, Anogeissus leiocarpus, and Diospyros mespiliformis. Tree selection may reflect structural properties, leaf availability, and canopy cover. Chimpanzees selected taller trees with denser canopy cover prior to rainy nights.

How do arboreal insects maintain stable nest temperatures?

Arboreal ants combine passive and active thermoregulatory strategies. Passive strategies derive from nest architecture and moisture gradients within the nest, while active strategies involve foraging patterns and worker polymorphism. Internal nest temperature remained buffered relative to external fluctuations, and moisture was significantly higher at the nest's lower extremity. Worker size distribution shifted between day and night, indicating behavioral adjustments to thermal demands.

Why are tree nests important for conservation?

Tree nests serve as indicators of habitat use, population density, and ecosystem health. Chimpanzee nest surveys provide data for population estimates and conservation programs. Nest predation has increased at many northern locations due to climate change, affecting reproductive success of migratory birds. Arboreal termite nests support diverse symbiont communities whose abundance is shaped by nest volume. Protecting tree-nesting species requires maintaining suitable nesting trees and habitats.

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References and Further Reading

• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.
• Nests and nest building in birds.. Current biology : CB, 2022.
• Terrestrial nest-building by wild chimpanzees (Pan troglodytes): implications for the tree-to-ground sleep transition in early hominins.. American journal of physical anthropology, 2012.
• Sleep and nesting behavior in primates: A review.. American journal of physical anthropology, 2018.
• Developmental and Sex-Based Variation in Nest Building Among Wild Immature Chimpanzees.. American journal of primatology, 2025.
• Animal migration to northern latitudes: environmental changes and increasing threats.. Trends in ecology & evolution, 2022.
• Nest-Building Behaviour by Chimpanzees (Pan troglodytes verus) in the Non-Protected Area of Diaguiri (Kedougou, Senegal): Implications for Conservation.. Folia primatologica, international journal of primatology, 2018.
• Observational social learning of "know-how" and "know-what" in wild orangutans: evidence from nest-building skill acquisition.. Communications biology, 2025.
• Convergent evolution of elaborate nests as structural defences in birds.. Proceedings. Biological sciences, 2022.
• Thermal Ecology and Homeostasis in Colonies of the Neotropical Arboricolous Ant Azteca chartifex spiriti (Formicidae: Dolichoderinae).. 2025.
• Nest volume shapes termitophile abundance in Constrictotermes cyphergaster colonies. 2026.
• First evidence of underground extractive tool use by chimpanzees in Kibale National Park, Uganda.. 2026.
• Ulyxes, a new Australopapuan mite genus associated with arboreal nests (Acari: Laelapidae).. 2014.
• Forgotten reservoirs: an attempt to revive field research on rodent malaria parasites in their main natural host, the thicket rat Grammomys poensis (formerly Thamnomys rutilans). 2026.
• Evaluation of tree frog tracking methods using Phyllomedusa trinitatis (Anura: Phyllomedusidae). Phyllomedusa: Journal of Herpetology, 2018.
• Thermal adaptation and the potential anticipation of overnight weather in the nesting decisions of chimpanzees.. Current Biology, 2026.
• Embryo, Relocation and Secondary Nests of the Invasive Species Vespa velutina in Galicia (NW Spain). Animals, 2022.
• Особенности экологии и биологии размножения сизоворонки Coracias garrulus L., 1758 в Ставропольском крае. Ecosystem Transformation, 2023.
• Culture and variation in wild chimpanzee behaviour : a study of three communities in West Africa. 2003.
• A Ghost of a Chance. 2015.
• Tardigrades in the Forest Canopy: Associations with Red Tree Vole Nests in Southwest Oregon. Northwest Science, 2020.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.