What is the starling resistant entrance hole?

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The starling resistant entrance hole is a specifically sized and shaped opening designed to allow smaller, desirable birds like bluebirds and wrens access to nest boxes while preventing larger, more aggressive European starlings from entering. It is a crucial tool in promoting native bird populations.

Introduction to Starling Resistant Entrance Holes

European starlings are an invasive species known for aggressively outcompeting native birds for nesting cavities. They are larger than many desirable cavity-nesting birds and will readily evict them from nests, sometimes even killing nestlings. Therefore, providing appropriate housing with the right entrance hole is vital. What is the starling resistant entrance hole? It’s a simple yet effective solution that helps promote biodiversity by protecting vulnerable native bird populations. These entrance holes exploit the difference in size and body shape between starlings and the birds we want to encourage, acting as a selective barrier.

The Science Behind the Design

The effectiveness of a starling resistant entrance hole hinges on the starlings’ physical limitations. Starlings have a larger body size and a different skull shape compared to birds like bluebirds, wrens, and chickadees.

Size Matters: Starlings are generally larger than bluebirds. This size difference allows for an entrance hole size that admits bluebirds but is too small for starlings to comfortably enter.
Shape Plays a Role: While round holes are traditionally used, oval or crescent-shaped entrances are often more effective because starlings struggle to navigate these shapes.
Placement is Key: Placing the entrance hole higher on the nest box can also deter starlings, as they tend to prefer entrances lower down.

Different Types of Starling Resistant Entrance Holes

There are several different designs, each with its own advantages:

Round Hole: The most common type. A 1 1/2 inch diameter hole is generally effective for bluebirds while excluding starlings.
Oval Hole: A horizontal oval shape (e.g., 1 3/8 inches high by 2 1/4 inches wide) is often more effective than a round hole because it is more difficult for starlings to negotiate.
Crescent-Shaped Hole (or “NABS” hole): This design, championed by the North American Bluebird Society, is often very effective. It features a narrow horizontal slit at the top.
Slot Entrance: A narrow, horizontal slot can also be used, providing access for smaller birds while excluding starlings.

Benefits of Using Starling Resistant Entrance Holes

The advantages of using these specialized entrance holes are numerous:

Protects Native Bird Populations: Prevents starlings from outcompeting native birds for nesting sites.
Increases Nesting Success: Improves the chances of native birds successfully raising their young.
Promotes Biodiversity: Helps maintain a healthy and diverse bird population in your area.
Simple and Cost-Effective: Relatively inexpensive and easy to implement.

Common Mistakes to Avoid

While generally straightforward, certain mistakes can reduce the effectiveness of a starling resistant entrance hole:

Using the Wrong Size: An entrance hole that is too large will allow starlings to enter, defeating the purpose. Too small, and you’ll exclude your target species.
Poor Placement: Placing the hole too low makes it easier for starlings to access.
Lack of Monitoring: Regularly check the nest box for signs of starling activity.
Neglecting Maintenance: Ensure the hole remains clear of obstructions and the box is structurally sound.

Choosing the Right Entrance Hole for Your Area

The best choice depends on your specific location and the target species you want to attract. Researching the specific bird species in your area and their preferred nesting habits is crucial. Consulting with local birding groups or conservation organizations can provide valuable insights.

Entrance Hole Type	Diameter/Dimensions	Target Bird Species	Starling Resistance
——————-	———————————-	——————-	——————–
Round	1 1/2 inches	Eastern Bluebird	Moderate
Oval	1 3/8″ H x 2 1/4″ W	Eastern Bluebird	High
Crescent	Varies (Consult NABS guidelines)	Eastern Bluebird	Very High

Constructing and Installing a Nest Box with a Starling Resistant Entrance Hole

Building your own nest box is a rewarding project.

Choose the Right Materials: Use untreated wood such as cedar or pine.
Cut the Wood: Follow a nest box plan specific to your target bird species.
Drill the Entrance Hole: Carefully measure and drill the correct size and shape of the entrance hole.
Assemble the Box: Use screws or nails to assemble the box securely.
Install the Box: Mount the box on a pole or tree, facing away from prevailing winds. Ensure predator guards are in place.

Maintenance of Nest Boxes

Regular maintenance is essential for the continued effectiveness of your nest box.

Clean Annually: Clean out the nest box after the nesting season to remove old nests and debris.
Inspect Regularly: Check for damage or wear and tear.
Repair as Needed: Repair any cracks or damage promptly.

Frequently Asked Questions

Why are European starlings considered a problem for native birds?

European starlings are an invasive species that aggressively compete with native birds for nesting cavities. They are larger and more assertive, often evicting native birds from their nests or even killing nestlings.

What is the specific size of a round starling resistant entrance hole for bluebirds?

A round entrance hole with a diameter of 1 1/2 inches is generally considered a starling resistant entrance hole for bluebirds. This size allows bluebirds to enter while being too small for most starlings.

How does the shape of the entrance hole impact its effectiveness?

Oval or crescent-shaped entrance holes are often more effective than round holes because starlings struggle to navigate their unusual shapes. This shape presents a physical challenge for the starling’s larger skull.

Can I use a starling resistant entrance hole to attract other bird species besides bluebirds?

Yes, a starling resistant entrance hole can also attract other smaller cavity-nesting birds such as wrens, chickadees, and titmice. However, ensure the hole size is appropriate for the target species.

Where should I place the entrance hole on the nest box?

Placing the entrance hole higher on the nest box (typically 6-8 inches from the bottom) can deter starlings, as they tend to prefer entrances lower down.

How can I monitor the nest box for starling activity?

Regularly check the nest box for signs of starlings, such as starling feathers or nesting material inside. You may also observe starlings attempting to enter the box.

What materials are best for building a nest box with a starling resistant entrance hole?

Use untreated wood such as cedar, redwood, or pine. Avoid using treated lumber, as the chemicals can be harmful to birds.

How often should I clean out my nest box?

Clean out the nest box once a year, ideally after the nesting season has ended. This removes old nests and debris, preventing the buildup of parasites and diseases.

What should I do if starlings are still using my nest box despite the starling resistant entrance hole?

If starlings are still using the box, try blocking the entrance for a few days to discourage them. You can also try switching to a different type of starling resistant entrance hole like the crescent-shaped “NABS” hole.

Are there any disadvantages to using a starling resistant entrance hole?

In rare cases, a starling resistant entrance hole might exclude some larger native birds that could potentially use the box. However, the benefits of protecting native birds from starling competition generally outweigh this risk.

Where can I find plans for building a nest box with a starling resistant entrance hole?

Many resources offer nest box plans, including the North American Bluebird Society (NABS), local birding organizations, and online conservation websites.

How else can I help protect native birds from starlings?

In addition to using a starling resistant entrance hole, you can help by reducing food sources that attract starlings, such as open compost piles or easily accessible pet food. Also, ensure that other feeders use starling-proof designs.