Birdhouses: The Hole Story

Photo of Black-capped Chickadee by Skip Russell


There are a good number of backyard birds who nest in cavities, either holes they made themselves or ones they found already made.  Many will readily adapt to using a birdhouse or nest box, as it is also called.

Cavity-nesters in our area include: chickadees, nuthatches, wrens, bluebirds, swallows and woodpeckers.  Less common, but also locally housed are: Western Screech-Owls, Northern Saw-whet Owls, Barn Owls, American Kestrels and Wood Ducks.

 Chickadees, nuthatches and woodpeckers can, and often will, excavate their own cavity in a dead part of a branch or tree trunk. Putting shavings in a birdhouse for them to remove, satisfies these birds’ desire to excavate their own nesting site.  Having birdhouses built to species specifications will help your success.

Wrens will readily nest in birdhouses but do not excavate their own. In bird-speak birds that nest in cavities but don’t do the digging are called secondary cavity nesters. Wrens prefer a comparatively shallow cavity, but are industrious and more than willing to bring in enough nesting material to raise the floor to their liking. In fact, male wrens may build more than one nest to try and attract a female.

Bluebirds and swallows, also are secondary cavity nesters. Without birdhouses, they would need to find an abandoned natural cavity to move in to. By the time these birds begin nesting, many natural cavities are already taken by non-native sparrows and starlings who begin nesting much earlier. Bluebirds and swallows prefer open, lightly-wooded or forest-edge areas. Farm pastures, new subdivisions with adjacent fields, school grounds, golf courses, or road rights-of-way are all good sites. If House Sparrows are a problem, remove the sparrow nest and plug entrance holes until the sparrows move on.

If a pair of birds is inclined to raise a second brood, many will not use the same birdhouse back-to-back. All of our cavity nesters defend a space around their nesting site –being particularly territorial against their own kind.  Placing multiple birdhouses around your yard can encourage more diversity in cavity nesters as well as offering your nesting pair a place to raise a second brood.

House Finches, American Robins, and Barn Swallows won’t use a birdhouse, but may take you up on a well-placed nesting shelf.

The rest of our songbirds make cup-nests or variations thereof.  Don’t miss out on the fun of offering natural nesting materials, as American and Lesser Goldfinches, Bushtits, Pine Siskins and more will be looking for natural fibers (such as our locally-grown pygora goat fleece), to build a water-tight nest. Put out nesting material in early February so birds may pull from it, even into mid-June.

Tips:  Whether you build or shop or a birdhouse, here are a few tips for greater success…

  • Avoid birdhouses with perches – predators will use it
  • The entrance hole must be large enough to allow the target species in, but small enough to exclude larger species from entering that same cavity.
  • The box should be easy to open for cleaning
  • Rust-proof screws or galvanized nails increase the life of a birdhouse
  • A roof with slight eaves and small drainage holes in the base provide protection to the nest against rain
  • Offer nesting materials, such as our locally-grown pygora goat fleece or natural plant fibers – but place them close to your window and away from your birdhouses.

A nest box project this February is a relatively simple way to become personally involved in bird conservation. Once birds move in, be prepared for hours of fun and fascinating bird watching!