BIRD
HOUSE DESIGN
How elaborate you make your bird house
depends on your personal sense of aesthetics. For the most
part, all the birds care about is their safety and the right
dimensions: box height, depth and floor, diameter of entrance
hole, and height of hole above the box floor. Refer to the
following chart, keeping in mind that birds make their own
choices, without regard for charts. So don't be surprised when
you find tenants you never expected in a house you intended
for someone else.
Nest
Box Dimensions
Box
Box
Entrance Entrance Placement
floor
height height
diameter height
Species
inches inches
inches
inches
feet
===============================================================
American
Robin*
7x8 8
---
--- 6-15
---------------------------------------------------------------
Eastern &
Western
Bluebird
5x5
8-12
6-10
1-1/2
4-6
---------------------------------------------------------------
Mountain
Bluebird
5x5
8-12
6-10
1-1/2
4-6
---------------------------------------------------------------
Chickadees
4x4
8-10
6-8
1-1/8
4-15
---------------------------------------------------------------
Titmice
4x4
10-12
6-10
1-1/4
5-15
---------------------------------------------------------------
Ash-throated
Flycatcher
6x6
8-12
6-10
1-1/2
5-15
---------------------------------------------------------------
Great
Crested
Flycatcher
6x6
8-12
6-10
1-3/4
5-15
---------------------------------------------------------------
Phoebes*
6x6
6
---
---
8-12
---------------------------------------------------------------
Brown-headed
Pygmy and
Red-breasted
Nuthatch
4x4
8-10
6-8
1-1/4
5-15
---------------------------------------------------------------
White-
breasted
Nuthatch
4x4
8-10
6-8
1-3/8
5-15
---------------------------------------------------------------
Prothonotary
Warbler
5x5
6
4-5
1-1/8
4-8
---------------------------------------------------------------
Barn
Swallow*
6x6
6
---
---
8-12
---------------------------------------------------------------
Purple
Martin
6x6 6
1-2
2-1/4 6-20
---------------------------------------------------------------
Tree and
Violet-Green
Swallows
5x5
6-8
4-6
1-1/2
5-15
---------------------------------------------------------------
Downy
Woodpecker
4x4
8-10
6-8
1-1/4 5-15
---------------------------------------------------------------
Hairy
Woodpecker
6x6
12-15
9-12
1-1/2
8-20
---------------------------------------------------------------
Lewis's
Woodpecker
7x7
16-18
14-16
2-1/2
12-20
---------------------------------------------------------------
Northern
Flicker
7x7
16-18
14-16
2-1/2
6-20
---------------------------------------------------------------
Pileated
Woodpecker
8x8
16-24
12-20
3x4
15-25
---------------------------------------------------------------
Red-Headed
Woodpecker
6x6
12-15
9-12
2
10-20
---------------------------------------------------------------
Yellow-
bellied
Sapsucker
5x5
12-15
9-12
1-1/2
10-20
---------------------------------------------------------------
Bewick's and
House wrens
4x4 6-8
4-6
1-1/4 5-10
---------------------------------------------------------------
Carolina
Wren
4x4 6-8
4-6
1-1/2 5-10
---------------------------------------------------------------
Barn Owls
10x18 15-18
4 6
12-18
---------------------------------------------------------------
Screech
Owls and
Kestrel
8x8
12-15
9-12
3
10-30
---------------------------------------------------------------
Osprey
48x48 platform
---------------------------------------------------------------
Red-tailed
Hawk and
Great
Horned Owl
24x24 platform
---------------------------------------------------------------
Wood Ducks
10x18 10-24
12-16
4 10-20
---------------------------------------------------------------
*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, susceptibly to predators, and
ease of maintenance.
Ventilation
Without air vents, boxes can turn into
bird ovens. There are two ways to provide ventilation: leave
gaps between the roof and sides of the box, or drill 1/4"
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 by
drilling 1/4 inch holes in the box floor. Nest boxes will last
longer if the floors are recessed about 1/4 inch.
Entrance
Hole
Look for the entrance hole (and exit)
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 those beautiful
duplexes or houses that have more than one entrance hole. With
the exception of purple martins, cavity-nesting birds prefer
not to share a house. While these condos look great in your
yard, starlings and house sparrows are the only birds inclined
to use them.
Accessibility
Bird houses should be easily accessible
so you can see how your birds are doing and, when the time
comes, clean out the house.
Part of being a responsible bird house
landlord is your willingness to watch out for your tenants.
Monitor your bird houses every week and evict unwanted
creatures: house sparrows, starlings, rodents, snakes, and
insects.
Be careful when you inspect your bird
boxes. You may find something other than a bird inside. Don't
be surprised to see squirrels, a mouse, a snake, 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 grab the nearest can of insect spray. If
you do, use only insecticides known to be safe around birds:
1% rotenone powder or pyrethrin spray. If wasps are a problem,
coat the inside top of the box with bar soap.
Here's how to check your nest boxes:
Watch the nest for awhile. If you don't
see or hear any birds, go over and tap on the box. If you hear
bird sounds, open the top and take a quick peek inside. If
everything's okay, close the box. If you see problems
(parasites or predators), remove them and close the box.
Here's where 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. Just 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.
If you clean out your nest boxes after
each brood has fledged, several pairs may use the nest
throughout the summer. Many cavity nesting birds will not nest
again in a box full of old nesting
In the fall, after you've cleaned out
your nest boxes for the last time, you can put them in storage
or leave them out. Gourds and pottery last longer if you take
them in for the winter. You can leave your purple martin
houses up, but be sure to 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 be sure to clean out all
houses you've left out for the winter.
Limiting
Predator Access
Proper box depth, roof, and entrance
hole design will help minimize predator (raccoons, cats,
opossums, and red squirrels) access. Sometimes all it takes is
an angled roof with a three-inch overhang to discourage
mammals.
The entrance hole is the only thing
between a predator and a bird house full of nestlings. By
itself, the 3/4" wall isn't wide enough to keep out the
arm of a raccoon or house cat.
Add a predator guard a 3/4 inch thick
rectangular wood block, to thicken the wall, and you'll
discourage sparrows, starlings, and cats.
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