Species Box floor Box Entrance Entrance Placement
(inches) height height (inches) diameter
(inches) (inches) height
(feet)
American Robin[1] 7×8 8 —— ——
Eastern & Western 5×5 8-12 6-10 1½ 4-6
Bluebirds
Mountain Bluebird 5×5 8-12 6-10 1½ 4-6
Chickadee 4×4 8-10 6-8 1⅛ 4-15
Titmouse 4×4 10-12 6-10 1¼ 5-15
Ash-throated Flycatcher 6×6 8-12 6-10 1½ 5-15
Great Crested Flycatcher 6×6 8-12 6-10 1¾ 5-15
Phoebe[1] 6×6 6 —— —— 8-12
Brown-headed/Pygmy/ 4×4 8-10 6-8 1¼ 5-15
Red-breasted Nuthatch
White-breasted Nuthatch 4×4 8-10 6-8 1⅜ 5-15
Prothonotary Warbler 5×5 6 4-5 1⅛ 4-8
Barn Swallow[1] 6×6 6 —— —— 8-12
Purple Martin 6×6 6 1-2 2¼ 6-20
Tree and Violet-Green 5×5 6-8 4-6 1½ 5-15
Swallows
Downy Woodpecker 4×4 8-10 6-8 1¼ 5-15
Hairy Woodpecker 6×6 12-15 9-12 1½ 8-20
Lewis’s Woodpecker 7×7 16-18 14-16 2½ 12-20
Northern Flicker 7×7 16-18 14-16 2½ 6-20
Pileated Woodpecker 8×8 16-24 12-20 3×4 15-25
Red-Headed Woodpecker 6×6 12-15 9-12 2 10-20
Yellow-bellied Sapsucker 5×5 12-15 9-12 1½ 10-20
Bewick’s/House Wrens 4×4 6-8 4-6 1¼ 5-10
Carolina Wren 4×4 6-8 4-6 1½ 5-10
Barn Owl 10×18 15-18 4 6 12-18
Screech-Owl and Kestrel 8×8 12-15 9-12 3 10-30
Osprey 48×48 platform
Red-tailed Hawk/Great 24×24 platform
Horned Owl
Wood Duck 10×18 10-24 12-16 4 10-20
[1]_Use nesting shelf, platform with three sides and an open front_
Now that you have the correct dimensions for your bird house, take a
look at how to make it safe: ventilation, drainage, susceptibility to
predators, and ease of maintenance.
_Ventilation_
You should provide air vents in bird boxes. There are two ways to
provide ventilation: leave gaps between the roof and sides of the box,
or drill ¼ inch holes just below the roof.
_Drainage_
Water becomes a problem when it sits in the bottom of a bird house. A
roof with sufficient slope and overhang offers some protection.
Drilling the entrance hole on an upward slant may also help keep the
water out. Regardless of design, driving rain will get in through the
entrance hole. You can assure proper drainage by cutting away the
corners of the box floor and drilling ¼-inch holes. Nest boxes will
last longer if the floors are recessed about ¼ inch.
_Entrance Hole_
Look for the entrance hole on the front panel near the top. A rough
surface both inside and out makes it easier for the adults to get into
the box and, when it’s time, for the nestlings to climb out.
If your box is made of finished wood, add a couple of grooves outside
below the hole. Open the front panel and add grooves, cleats or wire
mesh to the inside. Never put up a bird house with a perch below the
entrance hole. Perches offer starlings, house sparrows and other
predators a convenient place to wait for lunch. Don’t be tempted by
duplexes or houses that have more than one entrance hole. Except for
purple martins, cavity-nesting birds prefer not to share a house.
While these condos look great in your yard, starlings and house
sparrows are inclined to use them.
_Accessibility_
Bird houses should be easily accessible so you can see how your birds
are doing and clean out the house. Monitor your bird houses every week
and evict unwanted creatures such as house sparrows or starlings.
Be careful when you inspect your bird boxes—you may find something
other than a bird inside. Don’t be surprised to see squirrels, mice,
snakes or insects. Look for fleas, flies, mites, larvae and lice in
the bottom of the box. If you find insects and parasites, your first
reaction may be to grab the nearest can of insect spray. If you do,
use only insecticides known to be safe around birds: 1 percent
rotenone powder or pyrethrin spray. If wasps are a problem, coat the
inside top of the box with bar soap.
[Illustration: Squirrel in nest box]
Here’s how to check your nest boxes for unwanted visitors:
Watch the nest for 20-30 minutes. If you don’t see or hear any birds
near the box, go over and tap on the box. If you hear bird sounds,
open the top and take a quick peek inside. If everything is all right,
close the box. If you see problems (parasites or predators), remove
them and close the box.
A bird house with easy access makes the job simple. Most bird houses
can be opened from the top, the side, the front or the bottom. Boxes
that open from the top and the front provide the easiest access.
Opening the box from the top is less likely to disturb nesting birds.
It’s impossible to open a box from the bottom without the nest falling
out. While side- and front-opening boxes are convenient for cleaning
and monitoring, they have one drawback: the nestlings may jump out. If
this happens, don’t panic. Pick them up and put them back in the nest.
Don’t worry that the adults will reject the nestlings if you handle
them. That’s a myth; most birds have a terrible sense of smell.
[Illustration: Cleaning house]
If you clean out your nest boxes after each brood has fledged, several
pairs may use the nest throughout the summer. Some cavity-nesting
birds will not nest again in a box full of old nesting material.
In the fall, after you’ve cleaned out your nest box for the last time,
you can put it in storage or leave it out. Gourds and pottery last
longer if you take them in for the winter. You can leave your purple
martin houses up, but plug the entrance holes to discourage starlings
and house sparrows.
Leaving your wood and concrete houses out provides shelter for birds,
flying squirrels and other animals during winter. Each spring,
thoroughly clean all houses left out for the winter.
_Limiting Predator Access_
Proper box depth, and roof and entrance hole design will help reduce
access by predators, such as raccoons, cats, opossums, and squirrels.
Sometimes all it takes is an angled roof with a three-inch overhang to
discourage small mammals.
The entrance hole is the only thing between a predator and a bird
house full of nestlings. By itself, the ¾-inch wall is not wide enough
to keep out the arm of a raccoon or house cat. Add a predator guard (a
¾-inch thick rectangular wood block with an entrance hole cut in it)
to thicken the wall and you’ll discourage sparrows, starlings, and
cats.