For decades, the staff at the Norcross Wildlife Sanctuary has worked to encourage the presence of bluebirds. Since the 1970’s, hundreds of local schoolchildren have visited each winter to construct his or her own nestbox and learn about the plight of the eastern bluebird. We have also provided nestboxes for free to neighbors and friends. Over the years we estimate that, tens of thousands of nestboxes have been given out in hopes of providing a safe place for bluebirds to nest in our area. And we are also doing our part by monitoring and maintaining a bluebird trail of 42 boxes.
What To Do With Your Nestbox
To attract bluebirds, select an open grassy area that has some trees nearby for perch sites. Areas with thick brush or shrubs will attract house wrens, a native songbird. Here at the Norcross Wildlife Sanctuary, we place our nestboxes in pairs to minimize competition from the native tree swallow. The two species will nest next to each other, but are very territorial and will not allow their own kind to nest near them. The two boxes should be between 10 to 15 feet apart. Additional box pairs should be 100 yards away, distance enough to accommodate territories established by nesting pairs.
The 1½” diameter hole in Norcross nestboxes is too small for starlings, but English sparrows nest in them readily. Where we have problems with sparrows, Slot boxes are erected. This style box does not prevent sparrows from nesting, but allows space for escape should a sparrow enter while another bird is inside.
Boxes should be installed 4 to 6 feet above the ground, and should face away from prevailing winds. Our boxes are mounted on steel poles with predator baffles. Although it is said that bluebirds prefer south facing entrances, we have found that our birds prefer boxes that are in an open sunny location, out of the wind. Do not put nestboxes in areas treated with pesticides or herbicides. Most of a bluebird’s diet is made up of insects, and these poisons travel up the food chain.
Do not be afraid to check your nestbox regularly. Clean the boxes out in late February or early March, and monitor the box weekly during the nesting season. Brief inspections will not cause nest abandonment, and actually benefit bluebirds. Avoid disturbing the birds during inclement weather, or after the nestlings eyes are fully opened and they develop their flight feathers. This may cause the birds to leave the nest prematurely.
Occasionally, blowfly larvae are found the nest. These larvae can become parasitic on the nestlings. If you do find blowflies, carefully remove the nest and nestlings, and clean the box. The adult bluebirds will NOT abandon their nests if you touch them.
If a wasp nest is found, try to remove it but use caution. If there is a baffle on the pole, you may want to check to see if wasps are underneath. They won’t harm the birds here, but the monitor may disturb them.
When you approach the birdhouse, always knock so the incubating mother can exit. Houses that are monitored regularly do well with a baffle present on the pole, as the human scent left behind will attract predators. If signs of predation appear, such as broken eggs or missing nestlings, you may want to check your baffle or consider relocating the house. Dead nestlings should be removed from the nest.
Once the fledglings are gone, remove the nest. If the box is in need of thorough cleaning, a mild bleach/water solution (1 part bleach/10 parts water) can be used. Otherwise just sweeping the box out with a wire brush will do. Boxes should be well ventilated and have drainage holes. We do not recommend painting or staining the box. Rough-cut lumber is preferred, as it is easier for the birds to cling to the box. Perches should never be placed on a nest box.
Other species that have successfully nested along our bluebird trail include tree swallow, black-capped chickadee, white-breasted nuthatch and house wren. These native species are protected by law and should not be removed. We have also had red and flying squirrels raise young in the nestboxes.
Boxes placed near buildings will be attractive to English sparrows or starlings. These nests should be removed as often as they are found. Both of these species are introduced and are not protected.
Below you’ll find a link for a bluebird nestbox that you can build on your own:
Photos thanks to Mike Benfield, John Doe, etc. (this is a simple example of an attribution).