Posted on Leave a comment

Birdhouse 101: Why Entrance Size Matters?

Birdhouses come in various sizes and features, but one factor that is often overlooked is the entrance hole size. The size of the entrance hole can influence which bird species use the house and provide protection to the inhabitants from predators. Moreover, the size of the entrance hole dictates the type of birds that can enter the birdhouse. Different bird species have different preferences when it comes to entrance hole size. It’s noteworthy that cavity-nesting birds generally prefer a smaller entrance hole size. Therefore, it’s important to select the right size for the bird species you’re hoping to attract.

Why Entrance Size Matters?

To make birds feel welcome, safe and comfortable in a birdhouse, the entrance size is critical. A smaller entrance hole will attract smaller birds, while a larger hole will attract larger birds. For example, a wren, titmouse, or chickadee will fit into a hole that is 1.125 inches in diameter, while a bluebird or tree swallow requires an entrance hole of 1.5 inches. If the entrance hole is too big, it allows predators like squirrels, raccoons, or snakes to attack eggs, nestlings and adult birds. Often, larger birds of prey like hawks and owls look for larger entrance holes when hunting. Therefore, to protect the bird family, it’s essential to select the appropriate hole size for the desired bird species.

Furthermore, choosing the right entrance hole size will ultimately play an important role in promoting bird conservation and creating a safe habitat for nesting birds. The entrance size is critical when trying to deter invasive species like the House Sparrow. The House Sparrow is an aggressive bird species that invade the nests of other birds, breaks their eggs, destroys their nests, or kills the nestlings. With their sharp beaks, they can easily enlarge holes to gain access to nests meant for other bird species. By selecting an entrance hole size that suits the desired bird species and keeping the hole at the appropriate size, it makes it more difficult for invasive species to enter, reducing the risk of predator intrusion.

How to Select the Right Hole Size?

Different bird species require specific entrance hole sizes, and the size of the hole is vital for the safety of the nesting birds. It’s essential to keep in mind that the hole size should also be adjusted based on the bird species’ requirements.

One of the important considerations when selecting the hole size of a birdhouse is the body size of the bird. Smaller birds can slip through smaller holes more easily than larger birds. Consequently, they have a better chance of fitting into the birdhouse, making it a suitable home. Additionally, birds with specialized beaks like the sapsucker require specific hole sizes to enter comfortably. However, open nesting birds such as robins, blackbirds, and thrushes construct their nests in open spaces, on branches, and shrubs. As a result, they are not as dependent on entrance hole size. What’s more, the entrance size should be appropriate for the weather conditions in your area. If you live in a region with heavy rainfall or strong winds, a smaller entrance might be better to keep the birdhouse dry and stable.

Round or Slot Entrance?

The birdhouse entrance doesn’t only vary in size but also shape. A round entrance is the most traditional type adopted in birdhouse design. It’s a circular hole, usually located near the top of the front panel. It’s suitable for a broad range of cavity-nesting birds, including sparrows, wrens, and bluebirds, while deterring large bird species like woodpeckers from entering the birdhouse. Statics show birds nesting in round-hole boxes produce significantly more eggs and have better fledging success. On the other hand, the slot entrance is a narrow rectangular opening neatly cut into the front panel of the birdhouse. It’s said to attract bluebirds while deterring competitor birds like House Sparrows. The slot entrance is also easier to make, as it does not require drilling a hole. But it can expose the nest to more predators, making it easier for them to reach in and attack the chicks. Moreover, it can create excess heat in the birdhouse during hot weather, which is unfavorable for young birds.

How to Resize a Birdhouse’s Entrance?

Most ready-to-make birdhouses normally have a predrilled hole that doesn’t necessarily match the optimum size of the birds you want to nest in your garden. To resize a birdhouse entrance, you’ll need a few tools and some basic woodworking skills.

If your birdhouse has an oversized entry hole, there are basically three solutions to make the adjustments.

Solution One: Cover Plates

The most direct method is to cover the original entry with a cover plate. Make sure the plate should is made of sturdy material like stainless steel and thick plastic, that can resist chewing, gnawing, or scratches. Cover plates usually come in dimensions like 28mm, 32mm, 35mm, etc. You should choose the proper dimensions for the birds that use the birdhouse. The cover plate should be screwed or nailed in place so it won’t fall off over time. And before you attach it to the birdhouse, smooth the rough edges around the hole’s rim so it will not injure the birds as they move in and out.

Solution Two: Hole Extenders

Adding a hole extender to create a small tunnel leading into the birdhouse is also a great way to narrow an enlarged entrance. The hole extender is a usually tube-shaped predator guard that fits around the entrance to extend the hole while discouraging predators from entering the birdhouse. Moreover, it also provides extra shelter from the weather. It is easy to attach it to the front of the house over the existing hole, just as a cover plate is attached. Although it is a less expensive form of predator protection and can be effective against predatory mammals, it does not protect against snakes.

Solution Three: New Panel with a New Entrance Hole

If the entrance hole is severely damaged and there’s no way to attach a predator guard to the birdhouse, it may be best to replace the entire front panel of the house. Then, you can crave an ideal entrance hole out of it. But you need to make sure the front panel is secure and not suffering from any cracks. A thick and sturdy front panel can also provide extra protection for nesting birds in bad weather.

But if the entrance hole is too small, you can also follow the instructions here to fix it:

Step 1: Determine the desired entrance hole size

Before you start resizing the entrance hole, you need to know the desired size for the bird species you are trying to attract. You can look up the specific bird you want to attract and find out its preferred entrance hole size.

Step 2: Measure the existing entrance hole

Use a ruler or tape measure to measure the diameter of the existing entrance hole. This will determine how much you need to cut out to resize the entrance.

Step 3: Mark the new entrance hole diameter

Using the measurements from step 1, place a piece of tape over the existing hole and mark the new hole on the tape. This will allow you to adjust the size until you are satisfied.

Step 4: Cut out the new entrance hole

Using a drill with a hole saw attachment, carefully cut out the new entrance hole. After cutting out the new entrance hole, use sandpaper to smooth the edges of the hole. This will prevent any splinters or rough edges that could injure the birds.

Step 5: Clean the birdhouse

Before putting the birdhouse back up, clean it thoroughly, which will ensure the birdhouse is free from any debris or bacteria that could harm the birds.

Leave a Reply