Birds choose to lay their eggs in a phenomenal variety of places—from bare rocks and ground to twig platforms to hanging baskets sewn together with spider silk. In forested areas, another option is the cavity nest.
Around 85 North American bird species raise their young in tree cavities. In some cases, the bird itself makes the hole. In other cases, it may enlarge cavities created by natural decay or by the activity of other birds.
Woodpeckers are among the best-known cavity nesters, but also help provide nesting holes for owls, swallows, nuthatches, and many others who may enlarge holes started by the woodpeckers. Here are photos of just a few cavity-nesting species that live near me in the Pacific Northwest United States.
Red-breasted Sapsuckers create dramatic rows of holes in tree bark, as seen below. They feed not only on the sap that flows, but also on the insects that the sap attracts.
This tiny Red-breasted Nuthatch is bringing a small grub to its young. Both parents tend to the babies.
I discovered this pair of Bewick’s Wrens bringing grassy nesting material into this natural tree cavity about 15 feet up a Cottonwood Tree:
The Northern Pileated Woodpecker is North America’s largest woodpecker, not counting the Ivory-billed Woodpecker, which is commonly believed to be extinct. Its holes are distinctly rectangular:
Below, a Black-capped Chickadee carries wood chips far from the hole where it cleared them—possibly a strategy to avoid a pile of chips that might call attention to the nest? Below right, a Tree Swallow stakes out a home for its family.