Half of all birds nest in tree cavities. Woodpeckers, owls, chickadees, nuthatches, and parrots are among the species that do.
Cavity nesters can be divided into several categories,
- those who excavate their own nests and don’t use abandoned holes (primary excavators)
- those who excavate and use natural or abandoned cavities
- those who don’t excavate but use natural or abandoned cavities – snags (secondary cavity nesters)
Remember: Good birders don’t disturb nesting birds. Observing nesting birds should be only done from inside a blind (like your house) or not at all.
Do-It-Yourselfers: Birds that excavate their own nests
Woodpeckers are the primary excavators of nest holes. Where the Northern Flicker is the primary nest cavity excavators, the Flicker’s nest holes provide homes to over thirteen species of mammal and bird species.
Some woodpecker species will choose living trees with solid hardwood to drill new nests. Other species will choose trees with wood softened by disease and fungal infestations. These primary nest hole builders include:
- Northern Flicker
- Pileated Woodpecker
- Red-bellied Woodpecker
- Red-headed Woodpecker
- Yellow-bellied Sapsucker
- Hairy Woodpecker
- Downy Woodpecker
Both male and female woodpeckers build nest holes. Most woodpecker species will excavate a new nest cavity every year. This provides plenty of abandoned cavities for other animals to use. Woodpeckers are supremely important to ecosystems for their excavation activities. Many woodpecker species are poorly studied. This means citizen scientists can help to fill in the gaps in research by collecting data.
Woodpecker nest holes can be identified by shape. The large Pileated Woodpecker makes a large squarish, oblong hole. The wood chips beneath the hole will be oblong, too. Wood chips are often used to line the nesting cavity. Hairy Woodpeckers make round holes.
Birds Who Excavate their Own Nest or Use Natural or Abandoned Cavities
Secondary nesters will build their nest on top of the old nests left in the hole. Snags (standing dead trees) with natural cavities are important to secondary cavity nesters. Secondary cavity nesters are the birds that will use human-made birdhouses.
Chickadees and nuthatch don’t have the powerhouse drilling bills of woodpeckers. But these little birds manage to drill their own nest cavities in the rotten wood of old trees.
- Black-capped Chickadee
- Carolina Chickadee
- Red-breasted Nuthatch
- Brown-headed Nuthatch
Birds who can’t excavate and only use natural or abandoned cavities
Some birds are unable to excavate their own nests. These species will locate and occupy abandoned woodpecker holes. The competition is fierce among these secondary cavity nesters to find and keep their nest holes. These birds will often use birdhouses.
- Brown Creeper
- Carolina Wren
- European Starlings
- Wood Ducks
- Common Goldeneye Duck
- Bufflehead Duck
- Barrow’s Goldeneye Duck
- Barn Owls
- Eastern Screech-Owl
- Great Horned Owl
- Northern Hawk Owl
- Elf Owl
- Barred Owl
- Long-eared Owl
- Boreal Owl
- Saw-whet Owl
- Purple Martin (in Western North America)
- Tree Swallow
- Tufted Titmouse
- White-breasted Nuthatch
- House Wren
- Winter Wren
- Prothonotary Warbler
On really cold nights, some birds have been known to seek the shelter of abandoned nest holes to survive the cold. Many birds will even gather together in holes for warmth.
Winter Nature Journal Activity Ideas
Find abandoned nest cavities in trees
- sketch the holes
- note whether the wood is living, rotten or diseased
- guess who made the hole
- guess the age of the hole
- guess who might live in the hole
I’d be careful looking into the hole. You don’t want to startle a Great Horned Owl with sharp talons.
And if you upload your sketch to the Internet, let me know. I would like to share it with your fellow naturalists. We would love to see it.