European Starlings in Nest Boxes: What Should You Do?
Quick answer: In North America, European Starlings can compete with native cavity-nesting birds for nest boxes. The good news is that, unlike House Sparrows, starlings are large enough that many boxes for smaller native species can exclude them simply by using the correct entrance-hole size. For boxes intended for larger native birds, prevention becomes more about placement, timing, monitoring and species-specific management.
This guide is specifically about European Starlings (Sturnus vulgaris) in North America, where they are introduced. In their native range, conservation context and management recommendations are different.
Cornell Lab’s NestWatch groups European Starlings with House Sparrows as non-native nest-box competitors in North America, but the practical problem is not identical. Starlings are much larger, which makes physical exclusion more effective for boxes intended for smaller cavity nesters.
First, Confirm That the Bird Is a European Starling
Do not manage a nest simply because a dark bird enters a cavity. Confirm the species first.
- Adult breeding starling: glossy dark plumage with green-purple iridescence, a long pointed bill and a short tail.
- Winter adult: dark plumage heavily spotted with pale tips.
- Juvenile: plain gray-brown with a long, pointed bill.
- Nest: usually built in a cavity with grasses, plant material, feathers and other soft material.
Cornell’s European Starling identification guide is a useful reference if you are uncertain.
The Biggest Advantage: Entrance Size Can Exclude Starlings
NestWatch states that European Starlings cannot squeeze through an entrance smaller than about 1½ inches. That means a correctly sized entrance can exclude starlings from boxes intended for many smaller native cavity nesters.
This is the most important difference from House Sparrows. House Sparrows can fit through much smaller openings, so there is no equivalent simple hole-size solution for most songbird boxes.
| Target box | Starling problem | Best first move |
|---|---|---|
| Small songbird box | Usually avoidable | Use the exact entrance size recommended for the target species and keep it below the starling threshold where appropriate. |
| Bluebird-sized box | Often avoidable | Do not oversize the entrance; use the species-specific bluebird dimensions. |
| Large-cavity species box | Harder to exclude physically | Rely more on placement, timing, monitoring and active management guidance. |
Do not make the hole smaller than the target native species requires. The purpose is to fit the intended bird correctly, not to improvise the smallest possible opening.
See OwlRatings’ birdhouse hole-size guide for species-specific sizing.
Why Oversized Entrances Create Avoidable Problems
If a box intended for a small native bird has an entrance larger than necessary, you may be giving starlings access for no benefit.
Before changing anything else, measure the entrance. A box with the wrong hole size can turn a simple design problem into a recurring competition problem.
If squirrels or wear have enlarged the opening, repair it with a correctly sized entrance plate rather than accepting the larger hole. OwlRatings’ guide to stopping squirrels from enlarging birdhouse holes explains that problem in more detail.
Larger Native Species Need a Different Strategy
Hole-size exclusion is less useful when the target native bird also needs a large entrance. NestWatch specifically notes that boxes for larger cavity nesters may require more active starling management because both species can fit through the entrance.
That means the decision should shift from “Can I shrink the hole?” to:
- Is this box in habitat that strongly favors the native target species?
- Can I delay opening or unplugging the box until the target migratory species returns?
- Can I monitor often enough to catch a takeover early?
- Am I unintentionally attracting starlings with nearby food?
Timing Can Reduce Early Starling Occupancy
NestWatch notes that European Starlings are resident in many areas and may claim nest sites before migratory native birds return. In some monitored nest-box systems, temporarily plugging boxes until the target migratory species is due back can reduce that head start.
This is not universal advice for every box. Resident native birds such as chickadees, titmice and nuthatches may also want cavities early, so use timing only when it fits the target species and local nesting community.
Feeding Choices Can Increase or Decrease Starling Pressure
NestWatch recommends reducing foods that strongly attract House Sparrows and European Starlings near nest-box areas. Mealworms, suet and scattered food can make a site more attractive to starlings, while feeder designs with shorter perches and smaller access ports may reduce use.
This does not mean all bird feeding must stop. It means a feeding station located beside a problem nest box can undermine your nest-box management plan.
Use a Four-Step Starling Management Sequence
| Step | Question | Action |
|---|---|---|
| 1. Identify | Is the occupant definitely a European Starling? | Confirm before intervening. |
| 2. Exclude | Can the target native species use a smaller entrance than a starling? | Use the correct smaller species-specific hole. |
| 3. Reduce attraction | Are box placement, timing or nearby food favoring starlings? | Change those conditions before escalating. |
| 4. Manage | Do starlings still occupy a large-entry box? | Follow current, legal, species-specific NestWatch guidance. |
This order keeps the simplest preventive fix first. A correctly sized entrance is easier, safer and more reliable than repeatedly reacting after a starling has already established a nest.
What If Starlings Have Already Started Nesting?
For U.S. readers, NestWatch states that European Starlings are not protected by the federal Migratory Bird Treaty Act because they are introduced. However, state, local and property-specific rules may still apply, and active management methods should never be generalized to protected native species.
Before taking action:
- Confirm the species.
- Check whether the box also contains an active native nest.
- Read the current NestWatch management guidance.
- Verify applicable state, local and property rules.
- Use the least disruptive effective approach you can maintain consistently.
Do Not Treat Every Nest-Box Competitor as a Starling
Native birds also compete for cavities. A native species occupying a box is not automatically a “pest” simply because it is not the bird you hoped for.
That distinction is especially important because many native birds, nests and eggs are federally protected in the United States. Management options that apply to introduced European Starlings do not automatically apply to House Wrens, chickadees, bluebirds or other native species.
If the problem species is a House Sparrow rather than a starling, use OwlRatings’ separate guide to House Sparrows in nest boxes. The exclusion problem is different enough to deserve its own strategy.
Audit the Box Before You Add Another One
When starlings repeatedly take over, adding more boxes is not always the solution. First check whether the current setup is structurally inviting them.
| Check | Why it matters |
|---|---|
| Entrance diameter | An unnecessarily large hole may give starlings access to a box meant for a smaller bird. |
| Target species | The entrance, box dimensions and habitat should be designed around one intended native species. |
| Placement | Some sites favor starlings more strongly than the native species you want. |
| Nearby food | Suet, mealworms or scattered food can increase local starling activity. |
| Monitoring frequency | Early takeover is easier to recognize when the box is checked consistently. |
For a low-disturbance checking routine, see how to monitor a nest box.
Bottom Line
For many small-bird nest boxes, European Starling problems can be prevented before they start by using the correct entrance-hole size.
That is the first thing to check. If the target native species needs a larger entrance too, move to habitat, timing, feeding pressure and consistent monitoring. If starlings still establish a nest, use current NestWatch guidance and verify local rules before active management.
Sources & Further Reading
- Cornell NestWatch — Managing House Sparrows and European Starlings
- Cornell NestWatch — Nest Box Learning Resources
- Cornell Lab — European Starling Life History
- Cornell Lab — European Starling Identification
- Cornell Lab — Eastern Bluebird Life History
Regional note: This management guide is written for North America, where European Starlings are introduced. In their native range, use local conservation guidance instead.
Jonathan Gron is the founder and editor of OwlRatings, where he researches birding, backyard wildlife and practical bird-safety guidance using current primary, government and professional sources.
