Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters

eggsName Ten Things That Are Wrong with this "Bluebird" Nestbox

First read Bluebird Basics - Do's and Don'ts.Then see if you can figure out at least 10 things that are wrong with this nestbox.


  1. The entrance hole is too big. A hole larger than 1.5" diameter will allow starlings and other predators to reach into the box.
  2. There are House Sparrows in the neighborhood. House Sparrows may destroy bluebird eggs and nestlings, and kill adults. It is better to have no box at all than to allow House Sparrows to reproduce in one. (See guidance on how to control House Sparrows.)
  3. The box has a perch. A perch invites House Sparrows.
  4. There is no overhang on the roof. Water could get through the entrance hole, wetting and chilling nestlings.
  5. The roof is not slanted to shed water.
  6. The box and roof are painted a dark color. This may cause the box to overheat, killing eggs or nestlings.
  7. The box does not have a predator guard on the pole to prevent raccoons, snakes and other predators from climbing it.
  8. The box is located on a fence, which acts as a predator highway.
  9. The box is too close to a brushy area that is House Wren habitat. House Wrens may puncture eggs of other birds, kill young nestlings, and fill up boxes with "dummy" stick nests.
  10. The box has no ventilation holes in the sides. This may cause the inside to get too hot.
  11. The box is too deep. Nestlings (especially Tree Swallows) may be unable to get out of the box when they are ready to fledge.
  12. The box is made of very thin material. Wood used to make nestboxes should be at least 3/4 - 1" thick.

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May all your blues be birds!

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Last updated March 24, 2016. Design by Chimalis.