Up to forty different species of backyard birds can successfully nest in bird houses, with the only real need being that the entrance hole be of a specified diameter.
The size of the hole in a bird house can range from 1 inch to 3 inches; some species of birds can use the same size hole to nest in multiple different types of bird houses. That works for spherical port openings, but it may also be a cup with a wide mouth. The hole sizes should be similar to what birds use in the natural, however this is not a strict requirement.
If you want to attract a certain kind of bird to your yard, you might want to know what size hole is typical in a bird house.
There are several factors to consider while putting together a bird house in order to entice a specific species, such as a Bluebird, a Wren, a Woodpecker, or an Owl.
My comprehensive guide to bird house hole sizes includes information for up to 43 species of birds found in the United States and adjacent regions of Canada.
If you don’t give careful thought to the size of the holes, the birds will arrive nonetheless, but you’ll soon learn that it doesn’t meet their demands.
That’s because birds are picky about the size and shape of their nesting holes, and they won’t use a box if the hole is too little or too big.
However, I would argue that it shouldn’t matter too much if the hole is somewhat smaller or larger.
Please feel free to peruse my guide on bird house entry hole sizes, which begins with a straightforward chart of hole sizes and progresses to a discussion of hole shape.
Contents
Bird house hole size chart
| Bird species: | Hole Size: | Hole Shape: | Natural Hole: |
| Ash-Throated Flycatcher | 1-9/16in | Rounded | Cavity |
| American Kestrel | 3in | Rounded | Cavity |
| American Robin | Open Cup | Rounded | Open |
| Barn Swallow | Open Half-Cup | Cup | Open |
| Barn Owl | 2-1/2 | Rounded | Cavity |
| Barred Owl | 8in | Rounded | Cavity |
| Barrow’s Goldeneye | 3-1/2 | Rounded | Cavity |
| Bewick’s Wren | 1-3/8in | Rounded | Cavity |
| Black-Capped Chickadee | 1-1/8in | Rounded | Cavity |
| Bufflehead Duck | 2-1/2 | Rounded | Cavity |
| Carolina Wren | 1-3/8in | Rounded | Cavity |
| Chestnut-Backed Chickadee | 1-1/8 | Rounded | Cavity |
| Common Goldeneye | 3-1/2 | Square | Cavity |
| Common Merganser | 4 x 5 | Square | Cavity |
| Downy Woodpecker | 1-3/8in | Rounded | Cavity |
| Eastern Bluebird | 1-1/2in | Rounded | Cavity |
| Eastern Phoebe | Open Cup | Cup | Open |
| Eastern Screech Owl | 3in | Rounded | Cavity |
| Eurasian Tree Sparrow | 1-1in | Rounded | Cavity |
| European Starling | 1-5/8 | Rounded | Cavity |
| Great Crested Flycatcher | 1-9/16in | Rounded | Cavity |
| Hairy-Headed Woodpecker | 2in | Rounded | Cavity |
| Hooded Merganser | 3 x 4 | Square | Cavity |
| House Finch | 1-1/2in | Rounded | Cavity |
| House Sparrow | 1-3/16in | Rounded | Cavity |
| House Wren | 1in | Rounded | Cavity |
| Juniper Titmouse | 1-3/8 | Rounded | Cavity |
| Mountain Bluebird | 1-9/16in | Rounded | Cavity |
| Mountain Chickadee | 1-1/8 | Rounded | Cavity |
| Northern Flicker | 2-1/2in | Rounded | Cavity |
| Northern Saw-Whet Owl | 2-1/2 | Rounded | Cavity |
| Prothonotary Warbler | 1-1/4in | Rounded | Cavity |
| Purple Martin | 2in | Rounded | Cavity |
| Red-Bellied Woodpecker | 1-3/4 | Rounded | Cavity |
| Red-Breasted Nuthatch | 1-1/8in | Rounded | Cavity |
| Red-Headed Woodpecker | 1-3/4 | Rounded | Cavity |
| Tree Swallow | 1-1/2in | Rounded | Cavity |
| Tufted Titmouse | 1-1/4in | Rounded | Cavity |
| Violet-Green Swallow | 1-3/8 | Rounded | Cavity |
| Western Bluebird | 1-9/16in | Rounded | Cavity |
| Wood Duck | 4in | Rounded | Cavity |
| Wood Thrush | Open Cup | Cup | Open |
| White-Breasted Nuthatch | 1-3/8in | Rounded | Cavity |
For up to 43 common backyard bird species in the US, we’ve laid down the ideal bird house dimensions on a handy specifications list.
You probably don’t want to encourage the ducks, geese, owls, and kestrels (all of which are birds of pray that nest in open forests) that can relate to you to set up nests in your backyard this year.
The hole size column is an extremely precise yet vital measurement in inches.
While the aforementioned dimensions are standard for circular holes in bird houses, three types of birds will only nest in a cup with a hole cut out of the bottom. Rather than being an actual house, this is only a cup fashioned out of stone and wood resin, with room for three more birds through a square hole in the bottom.
Whereas it is not directly relevant, I have taken the time to describe the several types of cavities in which birds of the wild make their nests. Birds that build nests in man-made structures like bird houses use an interior cavity, while birds that build nests in the open use an exterior one.
The open cup nest is completely spherical, while the half-cup nest isn’t.
It is not necessary to drill a rounded hole in the table for the ducks and geese listed there, although setting up boxes is typically done only by people who study and care for wild birds.
Bird-specific hole size
Although the shape and size of the entrance hole to a bird home can vary, some species of birds are limited to using specific types of buildings.
The size of the entrance hole in a bird house, whether purchased ready-made or hand-crafted, is a crucial determinant in whether or not the birds in your backyard will use the housing you provide.
Setting up a more standard hole size gives you the best chance of success in an otherwise challenging region, or in this case, a previously lengthy process of attracting birds to nest.
That implies you need to either buy or construct a birdhouse with an entrance hole of the appropriate size.
Use a single hole size on a bird house to attract the greatest variety of birds, rather than switching out the holes or replacing the entire front.
Common backyard birds in the United States, such as chickadees, wrens, and titmice, prefer bird houses with small entrance holes.
Nonetheless, larger native species like owls and woodpeckers prefer a bird house with a much larger entrance hole.
Hole size sharing species
Having a bird house that can accommodate multiple bird species is an advantage when trying to lure birds to nest in your yard.
This time, you just need to worry about one size of hole for bird houses.
- If the bird house in question has a floor size of 5 x 5 inches and a hole height of 6 inches, the hole size is 1-1/2 inches, which is suitable with the Bluebird and Tree Swallow’s.
- More backyard birds, such as Chickadees, Titmice, Nuthatches, Wrens, and the Downy Woodpecker, will be attracted to a birdhouse with a 1-1/4 inch hole size, a 4 x 4 inch floor, and a 6 inch high entry hole.
- The Saw-whet Owl, the Hairy Woodpecker, and the Red-headed Woodpecker are just a few of the species that have been known to use bird houses with entrance holes measuring 2.5 inches or less. Make sure the hole is 9 inches above the ground when you construct the 6×6 floor.
- Three holes are ideal, with the largest entry hole being 13 inches in height to entice predatory birds like the Screech-Owl and the American Kestrel, as well as the Northern Flicker. The minimum floor size is 8 inches by 8 inches, and the maximum hole height is 13 inches.
To sum up, species that nest in shared bird houses can be just fine using a box with a hole size that is larger or less than what was specified.
Applies to rounded holes
For ease of understanding, I’ll assume that you know that whenever I talk about bird house entrance hole sizes, I’m referring to ones with a spherical hole.
My chart’s rounded openings are a nod to the more conventional shapes of bird houses that cater to a variety of species.
You can use stone or wood epoxy to construct a half-cup or an open nest, but rounded hole bird houses are simpler to construct and can be found just about anywhere.
Wooden bird homes have entrance holes drilled into them for birds like bluebirds, wrens, and others, but the exact dimensions needed for the cup to be open enough might be tricky to determine.
In sum, the breadth and, by extension, the depth of a cup bird nest created by different artisans can vary widely.
My recommendation is to only put up a round birdhouse in your yard if you want birds to nest there.
In contrast, cup patterns attract so few birds that it won’t be worth your time unless you’re swamped by Barn Swallows or Wood Thrushes.
Hole sizes can vary
Hole sizes don’t have to be precisely measured, so don’t worry if my recommendations or those of the National Audubon Society don’t work.
Regardless, it’s important to give careful consideration to the size of the entrance holes of a bird house, since otherwise any and all birds could use it.
That can include more aggressive or invasive species, as well as those with malicious intent.
In urban locations, putting up a bird house with too large of a hole will entice rodent predators like squirrels and raccoons, which can lead to the theft of eggs and the death of young birds.
This is why it’s crucial to employ appropriate hole sizes for different types of birds in bird houses.
Birds won’t mind whether the hole in your bird home is slightly too big or too small, so don’t worry if you drill it out or buy one with an imperfect size.
The success of a bird house in your backyard will depend on whether or not the interior is small enough for the birds to feel comfortable, but all other criteria also matter.
Hole replicates nest in the wild
Cavities, or holes, are what birds use in the nature, thus it’s not necessary to make them a precise size for any species.
A cavity in a hollow tree, for instance, would be an ideal nesting spot for Eastern Bluebirds.
Therefore, bluebirds will only nest in holes that are sufficiently large for their bodies, allowing them to enter and escape with ease, while remaining small enough to prevent predators from getting inside.
That’s specifically about bluebirds, but it also applies to woodpeckers and other cavity-nesting birds.
Since cavities in trees rarely conform to the exact dimensions that birds require, the birds must often make up with less than ideal accommodations than those found in manmade bird houses, which typically feature uniformly sized and shaped entrances.
A bird home with a square or triangular shape can scare the birds away, but all you need is a bird house with a rounded contour, or best of – to attract birds of all shapes and sizes.
Reject invasive species
It is not unusual to have birds show interest in or even nest in a bird house that was not designed for those particular birds.
Expect a variety of birds to nest in the box, or at least express interest, and know that any suitable species will use it as a roost over the winter.
You should take steps to prevent unwanted guests, such as non-native birds of America like the House Sparrow, from moving in to your nesting box.
Because of the tremendous damage they may cause to nestlings and eggs, sparrows should never be able to utilize a bird house designed, instance, for a bluebird, which has a hole size of 1-1/2 inches.
Bluebirds and Tree Swallows need a hole size of 1-1/2 inches, therefore cutting it down to 1-1/15 inches can keep sparrows out.
Altering the size of the holes in the bird house might not be a foolproof method of protection, but it may have some beneficial effects.
A second strategy for discouraging unwanted species is to position the birdhouse in an area that is unattractive to the target species.
A bird house predator guard, either homemade or purchased, can assist reduce the overall size of the opening while protecting nesters from predators.
To summarize
Now that I’ve given you my comprehensive guide to bird house hole sizes, let’s quickly review the key points.
However, if you need an exact or close to hole size indicated in inches, you should consult the chart I included at the top of my post.
Bird houses designed for a particular species of bird are a thing and must be constructed with care.
If it’s too little or too big, you can drive away the birds you want to attract entirely, or you might attract a species that is pickier than the one you were hoping to attract.
A bird house with a hole size that can accommodate up to five bird species at once is a good choice if you’re trying to save money by purchasing simply one box rather than two.
The Chickadee, Titmouse, Nuthatch, Wren, and Downy woodpecker all like a hole size of 1-1/4 [1.4 in] so that they may nest comfortably in your tree.
My book focuses on resin-made nests with a wide open cup at a specified depth, while most books focus on wooden bird houses with a spherical aperture of varying sizes.
Birds will still use a bird house with an inconsistently sized entrance hole as long as the difference is within a tolerable range.
Most birds in the backyard nest in preexisting tree cavities, so there’s no need for perfection there.
