One excellent way to help native cavity-nesting birds survive and thrive is to put up a nestbox(es). If are going to make or purchase a nestbox, you can select one specifically designed for the species of bird you want to attract. Different size birds with different habits have different preferences when it comes to entrance holes, interior volume, dimensions, mounting, etc.
Birds are most likely to use a nestbox that approximates natural cavity choices.
There are many nestbox styles, each of which have their own pros and cons. No matter what species you are trying to attract, you should choose or build a box that is sturdy, has the right size entrance, will stay dry inside, opens for cleaning and monitoring. There are also many choices of material (wood, PVC, other) and a variety of types of predator protection.
If House Sparrows are common in your area, avoid a box with a perch, as it gives House Sparrows an unfair advantage. You should also monitor and maintain the nestbox.
NOTES ON HOLE SIZE:
- per Bergmann’s rule, some species of birds may be larger in colder climates – e.g., a Canadian starling may be bigger than a Florida starling, thus the Canadian bird might not be able to fit in a certain hole size that its southern version could squeeze into.
- Many people find that boxes with a 1.25″ or 1 1/8″ hole restrictor on them before an egg is laid are not utilized, even by smaller birds like titmice and chickadees.
- If the entrance hole is enlarged (e.g., by woodpeckers or chewing rodents), put a hole reducer on it.
Here are some commonly accepted birdhouse specifications (some sources disagree, so there may be multiple listings. Also, I do not know how reliable this information is – sometimes misinformation gets propagated).
Also see Nestbox Plans, Nestbox Styles – Pros and Cons, Bluebirding Basics, and Top Tips and Tricks for Attracting Bluebirds. REALLY useful website on Nestwatch.org with plans and recommended habitat, height and spacing.
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Species
Click on bird name for more info |
House
Floor (Inches) |
House
Depth (Inches) |
Hole
Above Floor |
Minimum
Diameter of Hole (Inches) |
Height
Above Ground |
| Bluebird-Eastern |
5 x 5″ |
9″ |
7″ |
1.5″-1 & 9/16″ |
3-6′ |
| Bluebird-Mountain |
6 x 6″ |
9″ |
7″ |
1 & 9/16″* or 1.375″ x 2.250″ oval |
4-10′ |
| Bluebird-Western |
5.5 x 5.5″ |
9″ |
7″ |
1 9/16″ or 1.375″ x 2.250″ oval |
4-10′ |
| Ash-throated Flycatcher |
6 x 6″ |
12″ |
8″ |
1.75″ |
3-20′ |
| Barn Owl – box plans (no porch/perch!) |
18 x 20″ |
15-18″ |
4″ |
elliptical 3″ high x 4″ wide |
8-10′ |
| Barred Owl |
14 x 14″ |
26-28″ |
21-23″? |
6-8″ |
15-30′ |
| Bewick’s Wren |
4 x 4″ |
6-8″ |
4-6″ or 7″? |
1.25 to 1.5″ |
6-10′ |
| Black-capped Chickadee |
4 x 4″ |
8″ |
6″ |
1&3/8″? 1&1/8? ? BCCH is larger than CACH |
4 -10′ |
| Brown-headed Nuthatch |
prefer large? |
4.5-8″ |
1.25″ |
5-20′ |
|
| Bufflehead |
7 x 7″? |
18-20″ |
16-18″ |
2.5-3″ |
5-15′ |
| Carolina Chickadee |
4×4 |
8″ |
6″ |
1&1/8-1.5″ ? CACH is smaller than BCCH |
5-6′ P |
| Carolina Wren |
4 x 4″ |
6 to 8″ |
4 to 6″ |
1.5″ |
5 -15′ |
| Chestnut Backed Chickadee |
1&1/8″ |
5-15′ |
|||
| Common (and Barrow’s?) Goldeneye |
10 x 12″ |
25″ |
20-23″ |
3″ high x 4″ wide |
20-30′ |
| Downy Woodpecker (roosting) |
4 x 4″ |
9-12″ |
6-8″ |
1.25-1.5″ |
6-20′ |
| Flicker, Northern |
7 x 7″ or |
16-18″ |
13″ |
2.5 -3″ |
6-20′ |
| Great Crested Flycatcher |
6 x 6″ |
8-10″ |
6-8″ |
1.5-2.5″ |
8-20′ |
| Hairy Woodpecker |
6 x 6″ |
12-15″ |
9-12″ |
1.5-2.75″ |
12-20′ |
| Hooded (and common?) Merganser |
9 x 10″ |
25″ |
18″ |
3.5 x 4″ |
3-20′ |
| House Finch | |||||
| House Wren |
4 x 4″ |
6-8″ |
4-6″ or 7″? |
1-1.5″ |
6-10′ |
| Kestrel, American |
8 x 8″ |
16 to 18″ |
13 to 15 |
3″ |
10-30′ |
| Lewis’s Woodpecker |
7-7″ |
16-18″ |
14-16″ |
2.5″ |
12-20′ |
| Lucy’s Warbler |
1.25″
|
8.7′ (3 to 40′?)
|
|||
| Mountain Chickadee |
1.25″? |
4-10′ |
|||
| Prothonotary Warbler |
4 x 5.5″ |
8-10″ |
6-8″ |
1&1/8 to 1.25″ |
6-15′ |
| Purple Martin |
6 x 6″ |
6″ |
2″ |
2 to 2.5″. Use Starling Resistant Entrance Holes |
10-20′ |
| Pygmy Nuthatch |
4×4″ |
8-10″ |
6-18″ |
1.25″ |
5-15′ |
| Pygmy Owl |
6×8″ |
10-15″ |
9-13″ |
2.5″ |
10-20′ |
| Red-bellied Woodpecker |
6 x 6″ |
14″ |
11″ |
2″ |
20′ |
| Red-breasted Nuthatch |
4 x 4″ |
8-10″ |
6-8″ |
1&1/8-1.5″ |
12-20′ |
| Red-cockaded Woodpecker (Picoides borealis) |
Smear box with white paint and caulk to simulate dried sap. |
slope hole upward about |
15-18′ on tall longleaf, loblolly, and pond pine with low understory |
||
| Red-headed Woodpecker |
6 x 6″ |
12-15″ |
9-12″ |
1.75-2.75″ |
12-20′ |
| Saw-whet Owl |
6 x 6″? 7×7″? |
10-12″ |
8-10″ |
2.5-4″ |
12-20′ |
| Screech Owl |
8 x 8″ |
12-15″ 16″? |
9-12″ |
2.5 to 4″ |
10-30′ |
| Tufted Titmouse |
4 x 4″ |
8-10″ |
6-8″ |
1&3/8-1.5″ |
6-15′ |
| Tree Swallow |
6 x 6″ |
5″ |
5″ |
1 3/8?-1.5″ |
Will nest in boxes 5-5′ high |
| Violet-green Swallow |
5 x 5″ |
6″ |
1 to 5″ |
1.25-1.5″ round (prefer 1&3/8″?) |
10-12′ |
| White-breasted Nuthatch |
4 x 4″ |
9-11″ |
7-9″ |
1&1/8-1.5″ |
12-20′ |
| Wood Duck |
10 x 18″ |
10-24″ |
12-16″ |
3″-4″ |
10-20′ |
*Mountain Bluebird and Western Bluebird ranges overlap in some areas, and Mountain’s need a 1 9/16″ hole. Some Western’s are larger than others. So the 1 9/16″ hole is a safe bet, and will also exclude almost all starlings.
References and More Information:
- Nestbox Styles Pros & Cons
- Nestbox Access (Opening) Pros & Cons
- Mounting Styles, Pros & Cons
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The Birdhouse Network (Cornell)-nesting requirements and species bios
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Duncraft Bird House Nesting Box Specs
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Building and Locating Backyard Houses, 18 page University of Wyoming free booklet
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Peterson Field Guides-Eastern Birds’ Nest and Western Birds’ Nests, by Hal H. Harrison when information was not available from the two sources above (noted by a “P” after number)
- Nestbox Specifications-the proper size box for different bird species
- Building and Locating Backyard Houses, 18 page University of Wyoming free booklet
- Artificial Nesting Structures-Wildlife Management Institute-PDF version
- Cavity-Nesting Birds of North American Forests, USDA Forest Service
Bluebirders need to think “inside the box.”
-Doug Zimmerman
