What That Clump of Leaves in Your Tree Really Is. Hint: It’s Not a Bird’s Nest
As fall and winter descend and deciduous trees lose their leaves, you’ll see interesting structures in their branches. Clumps of leaves, branches, and moss may look like birds’ nests, but they’re not! Discover which furry creature makes these unique arrangements, and why they do so.

Contents
Many small critters make nests, which they use for protection, storage, and shelter. Nests are the animals’ homes. Just as we live inside houses we build, so do furry creatures in natural habitats. Each animal has its requirements for survival, and they make their homes according to what they need and want.
Birds require protection from ground-dwelling predators, so they build small, camouflaged nests high up in deciduous and evergreen trees. Their nests are typically small, round, and open on top, unlike the leafy clumps you’ve been seeing.
A resourceful, diligent, and sometimes crazy critter builds those awkward masses of leaves, wood, and other debris! It’s not a raccoon, a chipmunk, or a mouse! It’s a fuzzy, small rodent that loves eating nuts. Can you guess who it is yet?
The Short Answer

That’s right, the leafy clumps belong to squirrels! They’re the culprit. They amass dead wood, fall leaves, moss, and other animals’ nests to create a giant mess of debris. Inside, they assemble a den for themselves and their young. They live, eat, and store food in the structure, which naturalists call a “drey.” Dreys appear in many tree species across North America, wherever squirrels live and thrive.
The Long Answer
Different species use various trees depending on their specific needs. Learn which squirrels are native to your area, which trees they prefer, and how they construct their dreys. The more you know, the more likely you’ll be able to identify which ones live in your trees!
Squirrels Live in Dreys

Squirrels, like most small rodents, prefer a cozy little home to dwell in. They need protection from predatory birds and mammals and a place to store extra nuts and fruit. They often bury seeds and nuts. However, it’s always good to have a backup cache in case they forget where they buried them.
Dreys are unlikely homes, though, as they look shoddy and weak. Although they’re not as expertly crafted as wasps or birds’ nests, they do the job just fine. You’ll see dreys about 20 feet or higher on trees with nutritious nuts or seeds.
To construct dreys, these rodents gather materials like twigs, leaves, pine needles, cones, and anything else they can get their tiny hands on. They create an outer frame nestled between two branches for stability. Because a single drey will house many squirrels, the structures are usually about a foot or two wide with ample space for many family members.
Different Species Live in Different Trees

Many squirrel species live in North America. Each has its particular diet, habitat, and nest type. Find gray, red, brown, and flying species in forests throughout the country. Not every species constructs dreys, as some prefer using existing holes and caverns in trees and rocks.
Squirrels that commonly build dreys include the Eastern gray, American red, and flying types. Most other species prefer to live inside holes and cavities in tree trunks. Woodpeckers often leave large nests inside the bark. Otherwise, natural processes create cavities after branches break or trunks split. While rare, some species in cold habitats build nests underground!
While most prefer to live in tree cavities, some will build dreys if no such cavities exist. They’ll use the debris around them to construct a makeshift nest high on the tree. Eastern gray squirrels aren’t particular about tree type. They’ll build nests in a variety of tree species in both wild spaces and areas near people in eastern North America.
American red squirrels are a bit different. They prefer coniferous evergreen trees with plenty of cones. The cones contain delicious and nutritious seeds that they hoard in their drey. Their dreys are difficult to see, as evergreen branches often block them from view.
Pacific Northwest gardeners are lucky to have the Douglas squirrel around them. This type looks like the eastern gray, except it’s smaller and darker in color. The critters live in tree holes or constructed dreys, and they eat both conifer seeds and fungi. Because of this diet, they inadvertently plant new mushrooms and trees wherever they feed.
Squirrels Need Winter Shelter

Although squirrels build dreys, they don’t often live in them during the winter. Freezing temperatures, cold rains, and strong winds present constant threats to their cozy homes. The rodents retreat inside tree holes, underground burrows, or other animals’ nests during winter.
These furry creatures are unlike bears and birds—they don’t migrate, and they don’t hibernate during the cold months. They also don’t often spend the winter inside their dreys! The nests’ thin walls and high altitudes make them less-than-ideal winter homes.
Squirrels begin caching seeds, mushrooms, birds’ eggs, and any other food they can find starting in autumn. Some types, like the Douglas squirrel, build large storage structures separate from dreys called middens. These storage sites exist underground or inside tree trunks where they house food until the animals need it.
Others gather their resources in multiple, hidden locations. It’s best to leave these storage structures be if you find one. Without ample food security during winter, many rodents starve and die before spring abundance arrives.
After protecting their resources, the critters explore their environment to find a temporary winter shelter. They’ll reside inside holes in trees, rocks, and underground burrows. When these spaces are unavailable, some squirrels may remain in their dreys and suffer through the cold. They’ll congregate together to conserve warmth, and they may add extra insulating layers to their den.
Native Vs. Non-Native Species

Squirrels, like plants, have places of origin and preferred habitats. They may spread outside of their native range, causing troublesome issues for the other local species. Oftentimes we spread them into new states, as is the case with most invasive rodents in North America.
While the American red squirrel inhabits most states, the Eastern gray originates from temperate forests near the East Coast. It actively displaces the Western gray squirrel in suburban and urban areas throughout western states. The Eastern fox squirrel is another invasive species in the West; it has a large body and brown-red fur.
While all these species are native to North America, they each have their preferred habitats. When we spread them outside these ranges, they face new conditions that favor or hinder their continued growth. Often, a cold-hardy species from eastern regions moves to a western region where it dominates the ecosystem.
This scenario is the case for the Eastern gray squirrel, which settlers in Salem, Oregon brought to the state in 1918. Now, naturalists, horticulturalists, and environmentalists agree it’s best to keep invasive species out in order to preserve native plants, animals, and trees. They’ve found the Eastern gray squirrel displaces native populations five to ten years after it arrives.
How Can You Help?

So, what can you do to help squirrels in your community? Start by leaving dreys alone. The critters may build on them after winter if they survive the cold season. Leave other nests, burrows, and dens alone, too, just in case other animals are using them now or will in the future.
Help squirrels build dreys by providing ample nest-building material throughout the year. Leave deadwood, twigs, and branches in garden beds. The wood also fuels hungry fungi and mycorrhizae that thrive beneath the soil. Some other good drey materials include fall leaves, pine cones, and plant stems.
Aid your local animals further by leaving water saucers or dishes near the garden. Not only will thirsty squirrels appreciate the water, but so too will bees, ladybugs, and pollinating flies. Avoid leaving out nuts or food, as this causes squirrel populations to grow aggressive and human-dependent.
Two other easy ways to help are growing fungi and preserving oak trees or conifers. These three living things provide ample resources with edible mushrooms, acorns, and pine nuts. If a tree dies in your yard, leave it! Remove high branches so it’s safe, and leave the rest for squirrels to inhabit.
No matter what actions you take, you’ll be happy knowing that your local squirrels are safe and sound. Healthy squirrel populations lead to further environmental successes—more trees grow, more meat is available for predators, and less invasive plants take over.