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Once leaves drop in the fall, spotting nests in deciduous trees is easy. But birds likely didn’t build every structure you see: North American tree squirrels also construct treetop nests, called dreys. At first glance these mammal-made homes can resemble avian architecture, but once you know what to look for, you can easily tell them apart.

Squirrels

Although they prefer to den inside tree cavities (including old woodpecker hollows), gray, red, and fox squirrels all make dreys. The rodents usually choose a sturdy fork in a tree’s trunk or branches for their constructions, which are rather sloppy-looking and often nearly spherical, about a foot or two in diameter. A drey’s key giveaway is what it’s made of: mostly tree leaves. 

Crows

These clever corvids also build similarly sized, messy nests high in trees, but look closely: Crows weave theirs with twigs and thin branches, not foliage. While you can spot squirrels scurrying into dreys and dens year-round, crows use their nests only to raise their young. By fall, the birds will be long gone. 

Red-tailed Hawks

Like crows, these squirrel-eating raptors favor sticks for their nests, though they often incorporate leaves. Another clue to the architect’s identity: Squirrels typically build 20 to 40 feet above the ground, while Red-tails may aim considerably higher—as much as 120 feet in the air.

This story originally ran in the Fall 2025 issue as “Who Made That Nest?” To receive our print magazine, become a member by .