Deter House Wrens from Nestboxes

The house wren (Troglodytes aedon or HOWR) can be a very aggressive bird when it comes to nest site competition. It will remove or peck the eggs and destroy nests of other cavity nesters, driving them out of the area. In the case of nestboxes, house wrens can quickly drive out other birds, including songbirds such as the bluebird. Because they are protected under the Migratory Bird Act, it is illegal to hunt or trap house wrens or destroy an active nest. However, there are steps that you take to prevent house wrens from taking over your nestboxes and diminishing the variety of birds in your area.

Steps

Maintaining Nestboxes to Avoid House Wrens

1. Clean out dummy nests. House wrens create a number of nests, including dummy nests, in order to claim territory and ward off competitors. They also use dummy nests to cover the eggs and hatchlings of competitors, making it impossible for them to incubate their eggs or feed their young. Dummy nests consist of loose sticks, whereas an active nest has a lining of feathers and often eggs. Removing dummy nests makes it easier for other species to nest in a box.
   • It is illegal to remove an active house wren nest. Make sure it is a dummy nest before removing.
   • Removing dummy nests requires constant monitoring because house wrens will return and repeatedly try to rebuild them. Use a birdcam to watch the nestbox.
   • Do not drop sticks from dummy nest on the ground near the nestbox. House wrens will reuse the sticks if left nearby.
2. Remove old nests. House wrens often return to nestboxes with old nests, perhaps because they indicate a safe location from predators and competitors. If you want to make sure house wrens do not nest in a certain location, be sure to clean out any old nests at the end of the season.
   • House wren nests are usually empty by fall.
3. Plug the nestbox hole. If a nestbox has a dummy nest inside, place a cap over the hole to discourage house wrens from returning. This can be done with a rubber drain stopper or a piece of cork. Plugging a nestbox for a few weeks may convince local house wrens to move on to new territory and open up space for new tenets.
   • Although this may drive the house wrens away from one particular nestbox, it may also encourage them to move on to another one with birds actively nesting in it.
4. Use larger nestboxes. House wrens love tiny nestboxes, particularly the tiny ornamental birdhouses that can be found in many backyards. Multiple small boxes placed close together have a tendency to create large populations of house wrens and drive out other species. On the other hand, bigger boxes placed over a large area tended to facilitate the growth of other bird species.
   • It is believed that house wrens prefer the smaller floors of little nestboxes because they offer a better space for building their compact nests.
5. Try nestboxes with smaller holes. Slot, Gilbertson and Gilwood boxes have openings that make it easier for house wrens to fill them with sticks and create dummy nests. They also tend to have a smaller size that house wrens are drawn to. Use nestboxes with openings that make it difficult for house wrens to create dummy nests.
   • House wrens prefer a home with a diameter of roughly 1 1/8 inches. Making a hole smaller than this may prevent their entry.
   • Avoid gourd nestboxes, which also seem to attract house wrens.

Placing Nestboxes

1. Locate the box 200-300 feet away from woods or areas near rivers. House wrens prefer areas with lots of thickets, brambles, trees or shrubs. Placing nestboxes near house wren habitat, but not within it, will encourage their spread into the territory of other birds. Although the size of their territory is unknown, it is believed that house wrens may travel 100-230 feet from their nest site. Be sure to give yourself plenty of space between your nestbox and the nearby house wren habitat.
   • House wrens prefer nesting in deciduous trees, so place your nestboxes near conifers.
   • Remove shrubbery near the nestbox. You can also place nestboxes facing away from shrubbery. House wrens prefer shrubs over trees.
   • If possible, place boxes out in the open.
2. Mount nestboxes high. Although there is evidence that house wrens can nest between 10 and 30 feet, some birders claim that placing a nestbox above 12 feet will deter house wren nesting. This is believed to be because the height places the birds at a greater distance from shrubbery. This is common in urban settings where boxes along trails tend to be hung above 12 feet.
3. Remove extra boxes from endangered habitats. Taking down extra boxes will keep the number of house wren from exploding and minimize its impact on other populations. With fewer house wrens attacking their nests, other birds will be able to utilize the space.
   • Keep in mind that house wren territory may extend beyond 300 feet and that boxes beyond your property may attract house wrens to your area.
4. Place extra boxes without predator guards in house wren habitat. Placing extra boxes in house wren habitat will ensure that they do not steal them from other species. Removing the predator guard will also make it more difficult for house wren to safely nest and minimize the local population.
   • Eventually, removing the predator guards may also drive house wren into other areas. This may be more of a short term solution.

Using a Wren Guard

1. Make or purchase a Wren Guard. A Wren Guard is an L-shaped piece of wood that extends over the hole of a nestbox and obscures it from view. You can easily make a Wren Guard at home or purchase on from a retailer. It is believed to be effective because it makes it difficult for house wren to enter the box. The birds tend to perch on the roof before entering the nestbox, but this is difficult to do with the guard in place.
   • The guard should be made of the same material as the nestbox so that it blends in, but you can also make one of cardboard and plastic in a pinch.
   • Typically you have to make your own guard since the dimensions will be slightly different for each bird you are looking to protect. The space between the nestbox hole and the guard will vary depending on the bird nesting inside. However, there are some retail models available.
2. Watch the nestbox. Using a Wren Guard requires quite a bit of observation on your part. You need to pay attention to when birds begin nesting in the box so that you know when to attach the guard. The song of a house wren indicates that they have moved into the area and that you need to be vigilant.
   • Male house wren sometimes do not sing when entering a new area and remain unnoticed until they begin destroying nests.
   • Use a birdcam to keep a closer eye on your nestboxes.
3. Put the guard up after the desired bird has laid an egg or two. If you put the guard up too early, it is likely that the nesting birds will not return. If it is installed too late, a house wren may destroy the nest before you have a chance to stop it. The nesting birds need enough time to realize that they are in a safe space. Once they have laid a few eggs, they are invested in the space and much more likely to return.
   • Check the nest daily or install a birdcam to monitor it.
4. Remove the guard after the hatchlings are about a week old. The guard will make it difficult for the adult birds to feed the nestlings and may interfere with their eventual fledging. It may become more of a threat to the hatchlings than a house wren. At this point the baby birds will be too big for the house wren to throw from the nest or cover with twigs.
   • Chickadees and titmice nestlings need about two weeks before the guard can be removed.
   • For bluebirds, the guard can be removed 4-7 days after hatching.

Related Articles

• Make a Sparrow Nestbox
• Make an Eastern Bluebird Nestbox
• Build a Western Bluebird Nestbox
• Build a Chickadee Nestbox
• Build a Tufted Titmouse Nestbox

Sources and Citations

See also

• Build a Birdhouse
• Build a Bluebird House
• Build a Wood Duck House
• Make Perches for a Hummingbird Feeder