Keeping House Sparrows Out of Bluebird and Chickadee Boxes
Introduced House Sparrows take over nest boxes and kill native birds. Box design, placement, monitoring and legal management strategies that actually work.
8 min read · Updated 2026-09-28
- Legal status
- Non-native; not protected by the U.S. Migratory Bird Treaty Act
- Best exclusion
- 1 1/8 in hole for chickadees/wrens (too small for sparrows)
- Monitor
- Check boxes every 3–5 days in the breeding season
- Placement
- Open habitat, away from buildings and feeders
Why House Sparrows are a nest box problem
The House Sparrow (Passer domesticus) was introduced to North America from Europe in the 1850s and spread across the continent. It is a cavity nester that competes directly with bluebirds, Tree Swallows, chickadees, wrens and Purple Martins for the same holes. Unlike native competitors, sparrows frequently destroy eggs, kill nestlings and even kill incubating adult bluebirds inside the box, then build their own nest on top.
Because they are non-native, House Sparrows are not protected under the U.S. Migratory Bird Treaty Act, and in Canada they are not protected under the federal Migratory Birds Convention Act. That gives landlords of nest boxes room to manage them — but also a responsibility to identify birds correctly, because the native sparrows that look similar are fully protected.
Identify correctly before acting
Male House Sparrows have a grey crown, chestnut nape, black bib and whitish cheeks. Females are plain buff-brown with a pale stripe behind the eye and an unstreaked grey-brown breast. Their nests are bulky, domed masses of grass, feathers, trash and string that fill the box to the roof. Compare with bluebird nests (a neat cup of fine grass or pine needles), chickadee nests (a moss base with a fur-lined cup) and Tree Swallow nests (grass lined with feathers).
If you're unsure, do not remove anything. Removing an active native nest is illegal.
Location is your first line of defense
House Sparrows are tied to people: barns, farmyards, towns and feeding stations, especially where millet and cracked corn are scattered. The single most effective step is placing boxes away from these areas.
- Mount bluebird boxes in open habitat at least 100 ft from buildings, barns and livestock areas where possible.
- Avoid mixed seed with millet and cracked corn near nest boxes — sparrows love it; natives at your feeders don't need it.
- If sparrows are persistent at one spot, relocate the box rather than fighting it.
Box design choices
Entrance size is the only design feature that fully excludes sparrows. A 1 1/8-inch hole admits chickadees, House Wrens and Prothonotary Warblers but blocks House Sparrows. Bluebird holes (1 1/2 in) and martin holes are large enough for sparrows, so those boxes need management.
Some designs discourage sparrows without excluding them. Slot-entrance boxes and shallow boxes (such as the Gilwood or Peterson-style variations) are reported by bluebird trail monitors to be less attractive to sparrows in some areas, though results vary. Starling-resistant crescent entrances on martin housing exclude starlings but not sparrows.
Monitoring is the whole game
A box that isn't monitored during the season can become a sparrow factory, which makes the problem worse for every native bird in the area. Open and check boxes every three to five days from early spring through the end of the season. Knock gently before opening, and avoid checking when young are within a few days of fledging, when disturbance can cause premature departure.
If a House Sparrow nest is started, remove the nesting material each time you find it. Many sparrows give up after repeated removals, though determined pairs may persist. Record what you find; NestWatch, a Cornell Lab program, accepts nest box observations and publishes monitoring guidelines.
Deterrents with a track record
Monofilament "sparrow spookers" — a few strands of shiny mylar or fishing line hung over the box roof — are attached after the first bluebird egg is laid (never before, or bluebirds may abandon). Many bluebirders report that sparrows avoid the moving strands while bluebirds tolerate them. Remove spookers once young fledge.
- Pair boxes 5–25 ft apart in Tree Swallow areas so natives occupy both rather than leaving one open to sparrows.
- Plug or remove the entrance of unmonitored boxes outside your capacity to check.
- Clean boxes promptly after each brood fledges so they're ready for native second broods.
Trapping and humane removal
Experienced nest box monitors sometimes use in-box or ground traps to remove persistent House Sparrows. Because non-target native birds can be caught, traps must be checked frequently and any native bird released immediately. Local laws on trapping and dispatch vary; check your state or provincial wildlife agency's rules before starting, and consider working with a local bluebird society that can advise.
Frequently asked
Is it legal to remove House Sparrow nests?
In the U.S. and Canada, House Sparrows are non-native and not federally protected, so removing their nests is generally legal. Check state or provincial rules and be sure of identification — native sparrows are protected.
What hole size keeps House Sparrows out?
A 1 1/8-inch entrance excludes House Sparrows while admitting chickadees and wrens. Bluebird-size holes do not exclude them.
Will moving the nest box help?
Often. House Sparrows cluster near buildings, livestock and seed feeders. Moving boxes into open habitat away from these areas reduces takeovers.