One key consideration when building a birdhouse or nestbox is the size of the entrance, also known as birdhouse hole.
The diameter of your birdhouse entrance determines which birds can fit into the hole and use the house comfortably. No matter how appealing the nest may be, incorrect hole size is an instant turn-off to most birds.
Birdhouse diameter is also a crucial security feature, much like the regular doors and windows in our homes. If you go for an overly large entrance, you may find the birdhouse attracting all manner of birds, including undesirable species like birds of prey. Similarly, a tiny birdhouse entrance could make it difficult for larger birds to enter or exit the nest. In the process of forcing themselves in or out of the nest, the birds could damage their feathers.
So, when designing a birdhouse, it’s imperative to pay keen attention to the nest’s entrance. Of course, there are other important factors to bear in mind as well.
But how do you determine the right birdhouse entrance? That question shall be the focus of this post.
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How to Settle On the Right Birdhouse Hole Size
Many wild birds prefer their birdhouse or nestbox entrance holes to range between 1 inch and 2 inches in diameter. But as you shall find, the right birdhouse entrance hole largely depends on the specific bird species you’re building the house for.
In fact, nesting birds like chickadees, swallows, bluebirds, and wrens tend to be more particular about their house entrance holes. These birds prefer their nest entryways to be small enough to deter predatory birds or other animals that could be out to kill their hatchlings, and large enough to allow for seamless entry and exit into the nest. An inch too small or too large may be an instant turnoff.
Other birds are not only specific about the diameter of their nest entrance holes. They also prefer those nests to have certain designs.
For instance, barn swallows and robins prefer open-sided homes. Species like purple martins are more comfortable with crescent-shaped holes.
So, although we’ve already mentioned it, it warrants repeating that a birdhouse entryway should be designed with the needs of specific bird species in mind. That’s especially true if you’re trying to attract wild birds.
The following are some birdhouse entryway diameters recommended for common cavity nesting birds:
• Chickadees – 1 ¼ inches
• Flickers – 1 ¼ inches
• Nuthatches – 1 ¼ inches
• Titmice – 1 ¼ inches
• Warbles – 1 ¼ inches
• Woodpeckers – 1 ¼ inches
• Wrens – 1 ¼ inches
• Ash-throat flycatchers – 1 ½ inches
• Bluebirds – 1 ½ inches
• Red squirrels – 1 ½ inches
• Smaller songbirds – 1 ½ inches
• Tree swallows – 1 ½ inches
• House sparrows – 1 ¾ inches
• House finches – 2 inches
• Bufflehead ducks – 2 ½ inches
• Purple martins – 2 ½ inches
• American Kestrels – 3 inches
• Goldeneyes – 3 ½ inches
• Wood ducks – 4 inches
• Owls – 6 inches
What If You’re Unsure About the Birds to Attract?
It could happen that you’ve recently moved into a new home or location and are yet to find out the kinds of birds that nest around that area. When designing a birdhouse with no specific birds in mind, the conventional wisdom is to go for medium-sized holes.
It would be quite disappointing to build a 1 ¼ entryway, only to find out that owls are the most common birds nesting in that area. Similarly, building a 6-inch birdhouse entrance wouldn’t be ideal for smaller birds that might feel insecure nesting in houses with such huge entryways.
How about you start off with, say, a 2-inch hole size?
How Many Holes Should You Go For?
It’s intuitive to build just one entrance hole for your birdhouse. After all, birds typically don’t require emergency exits, right?
Well, you’re wrong.
Like all animals, birds feel safer nesting in houses with clear escape routes. Even birds of prey considered to be high up on the food chain, such as owls, eagles, and falcons, may still feel frightened nesting in houses with single entryways. That’s because they’re always in danger of being preyed upon by other animals, such as snakes, squirrels, bobcats, and weasels.
So, when designing a birdhouse, it’s important to consider having more than one hole.
Ideally, the holes should be located on opposite ends of the nest. That allows the nesting birds to make a quick escape through one hole as soon as they spot danger on the other entryway.
But safety isn’t the only reason to consider adding more entryways to your birdhouse.
Many holes also allow more than one adult bird to feed the hatchlings at the same time. Note that birds typically perch on the entryways to their nests while feeding their young. With a single hole, the other adult birds could be forced to waste time and energy flying around the nest until the feeding session ends and the hole is available for use.
Multiple birdhouse entrance holes is also an ingenious way to combat domineering chicks. Such chicks are notorious for blocking entryways so they can be fed first, or simply to prevent the other members of their brood from venturing outside the nest.
Last but not least, multiple entrances improve ventilation. Enhanced air circulation is crucial for birdhouses, particularly during warmer months.
Can Different Bird Species Use The Same Hole?
Unknown to many people, certain bird species can live in the same nest. That also means they’ll be using the same entryway.
Common nest-sharing birds include downy woodpeckers and house wrens.
Note that different bird species can only share the same living space if they feel safe and comfortable being around one other. So, if your birdhouse happens to attract more than one species, it’s useless trying to prevent other species from using the nest.
The best you can do as a responsible pet parent is to make the house habitable for all its occupants. That includes, among other things, designing an entryway that can fit both birds.
In this case, you’d need to come up with the right birdhouse hole bearing in mind the size of the larger bird. The good news is that most nest-sharing birds tend to be nearly the same size.
Alternatively, you may consider designing multiple entryways for the same birds. That way, each bird can use a hole tailored to its size.
Other Considerations When Designing a Birdhouse
a) Hole aspects
Birds can access their nests from all directions – above, below, or sideways. The exact position of a nest hole depends on what you’re looking to achieve.
Top entryways enhance sunlight penetration but are less efficient at ventilation. They also encourage flooding.
Bottom holes promote drainage but are risky as smaller chicks could accidentally drop off them.
Sideways holes are excellent for ventilation. But they too have their drawbacks, including poor drainage and reduced sunlight penetration.
The best way to go about this dilemma is to have multiple holes, preferably in different positions of the nest.
b) Perch requirements
Birdhouses do not necessarily require perches. That’s because most cavity-nesting birds are able to cling effortlessly on the outside of the nest.
In fact, perches tend to favor other predators more than the real nesters.
Just be sure to construct the house using wood as the material offers maximum grip.
c) Interior dimensions
A birdhouse should be large enough to encourage free movement of all the nesters.
On the flip side, avoid making the interior space too large as that could attract unwanted guests.
Wrap Up
Honing in on the right diameter for your birdhouse entryway depends on the specific bird species you wish to attract. If building a birdhouse with no specific nesters in mind, the convention is to go for medium-sized holes.
Also, be sure to consider other factors like the entryway aspect as well as the size of the interior space.
