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How to Keep Sparrows Out of Bluebird Houses

While several native bird species, such as tree swallows, house wrens, and chickadees, sometimes nest in bluebird boxes, house sparrows should be discouraged from using nest boxes whenever possible. House sparrows are not native birds. Not only do they compete with native species for nesting sites, they sometimes fight with and injure bluebirds, or even kill the bluebird adults or nestlings for whom the box was intended.

Things You'll Need

Clear fishing line - 6- to 20-lb weight
Push pins
Fishing weights or metal nuts

Instructions

- 1
  String vertical sections of fishing line tightly on either side of the nest box's entrance hole using push pins. For unknown reasons, this seems to deter house sparrows but not native birds. The Sialis website cites the Bluebird Society of Pennsylvania's recommendation to keep the line on either side of the entrance 1¾ inches apart.
- 2
  Hang additional lines from push pins inserted into the sides of the roof for added deterrence. Weight the dangling lines with a fishing weight or metal nut to prevent the line from being pulled into the nestbox, where it could injure nestlings.
- 3
  Insert pushpins into the four corners of the nest box roof and wrap fishing line around the outside, forming a square, then across both diagonals, forming an X across the roof. This prevents house sparrows from perching on the roof, which will make it more difficult for them to "claim" the box.
- 4
  Inspect your setup periodically and repair or replace fishing line that becomes degraded or broken. Loose fishing line could entangle and injure a young bird.

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