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Make 2017 your year to put up birdhouses

Birdhouses provide nesting places for native bird species including tree sparrows that eat lots of mosquitoes.
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Mountain Bluebird photo from http://www.audubon.org/field-guide/bird/mountain-bluebird.

By Janet Stafford and Margie Kaufman

Spring is here, and we look forward to the return of our summer birds.

We anticipate their arrival by preparing bird baths and waterers, setting up feeders and placing birdhouses for them to nest in.

There are many birdhouses available, but not all of them are suitable homes for birds.

In fact, some may be downright dangerous!

The only native birds found in the Cariboo that will use a birdhouse, also called a nest box, are cavity nesting birds like Mountain and Black-Capped chickadees, Tree Swallows, Violet-green swallows, White-breasted and Red-breasted Nuthatches, Wrens, Mountain Bluebirds and Northern Flickers.

Two non-native, invasive species that use birdhouses and often kill native birds to get to the birdhouse are House Sparrows and Starlings. The above mentioned birds, with the exception of the Northern Flicker, require cavities for nesting but they can’t excavate their own.

They rely on trees with old woodpecker holes or birdhouses.

A good birdhouse should have a door or lid that can be opened to remove the old nesting material.

If birdhouses are not cleaned out the nesting material builds up and puts the eggs and chicks closer to the opening.

This can allow jays, crows and ravens access the young and they eat them. The safest place for the eggs and chicks is in a proper birdhouse with a floor about eight inches below the opening.

The floor of the house, depending on the species, should be 4”x 4” to 4” x 8”

For instance the floor of a Chickadee house should be 4” x 4” while a Bluebird, Wren, or Swallow house should be 5” x 5” and a Flicker house is 5” x 8.”

Birdhouses with too large a floor space will mean that the bird will spend a long time building a nest to cover the floor, when she really didn’t need to spend that much time and energy!  And too small a floor can mean overcrowding for the chicks.

Another critical part of the birdhouse is that the inside door must be rough or  have a ladder sawn into the wood below the entrance hole so that the nestlings can get a foothold to get up to the opening.

If they can’t get a foothold they will not be able to get out and they will die.

The size of the entrance hole is also important. For chickadees the hole should be 1 1/8” in diameter. Since the floor space in a chickadee house is only 4” x 4”, their house is not suitable for larger birds whose chicks would be too crowded and a small 1 1/8” aperture will keep larger birds from nesting in it.

A Sparrow/Bluebird house should have a hold 1 3/16” to 1 ½” in diameter. The 1 ½” hole is small enough that the larger undesirable Starlings can’t enter the house.

Murderous House Sparrows (English Sparrows) can still gain access, though. Careful monitoring to see which species is using your house is a good idea.

And yet another point. The wood material must be thick enough to provide good insulation so that the interior of the box doesn’t get too hot or too cold.  Houses should be made from a minimum of 3/4” plywood. Anything thinner does not provide enough insulation.

Location of the bird house is important too.

Proper height from the ground, and distance from other houses is critical. Tree Swallow houses can be placed 20-25 feet apart, but Bluebird houses should be at least 300 feet apart.

Monitor the site for ants, as well. If an ant nest is below the tree or post where you place your bird house they may climb up into the box and kills the chicks. This can and does happen, so it’s important to watch out for ants.

Note that tree swallows eat a lot of mosquitoes. You might consider joining Williams Lake Field Naturalists at the Scout Island Nature Centre. As a member you would be able to purchase pre-made Bluebird/Swallow nest boxes for $10.

If you are interested in placing proper birdhouses on your property the following websites have good information on birdhouse dimensions and placement: http://www.sialis.org/nestboxguide.htm or http://www.nabluebirdsociety.org/nestboxes/nestboxplans.htm.