Nest-Box Competitors

House Sparrows and European Starlings
House Wrens
Native Wasps & Bees
European Paper wasps
Mice
Controlling Non-native Species

Introduction

Often nest boxes are not used by species for which they were intended. Wasps, mice and non-native bird species such as House Sparrows and European Starlings compete intensely and successfully with many native cavity-nesting species for nest sites, including nest boxes. Please include information about nest competitors in the online NestWatch data forms.

House Sparrows and European Starlings

House, or English, Sparrows and European Starlings are two abundant species introduced from Europe. House Sparrows, particularly the males, are extremely territorial and aren’t easily dissuaded from a particular area. To prevent either of these two species from taking up residence in your nest box, avoid putting boxes in areas where they occur in large numbers. Alternatively, put up nest boxes with entrance holes smaller than 1.5" in diameter that exclude House Sparrows but allow smaller species, such as chickadees and wrens to nest inside them.

House Sparrows and European Starlings are not federally protected so active measures can be taken to remove them from a nest box. Nevertheless, you must first be certain that the birds residing in the nest box are definitely starlings or House Sparrows.

To discourage these two species from taking residence in your boxes you can:

• Remove the nesting material as it is added.
• Boil or shake the eggs and return them to the nest. The effectiveness of this method is debatable. Sometimes females incubate the eggs for a long time, but other times females "catch on" and begin to re-nest immediately.
• Take down the nest box.
• Eliminate the adults. This is the most drastic measure that one can use. Adults can be live-trapped at the nest box and released some distance away. Some believe this only displaces the problem. Instead they prefer to live-trap the adults and deliver them to local raptor rehabilitation centers. There, these birds are fed to injured and recovering birds of prey.

A word of caution: Before taking any of these measures, it is important to consider the consequences of disturbing nesting House Sparrows. Removing a nest box may cause a House Sparrow to usurp a nest box from a neighboring pair of native birds and destroy the eggs or kill the nestlings.

House Wrens

Even House Wrens are sometimes considered problematic. These sprightly birds are very territorial and may use the same tactics as House Sparrows to evict nesting pairs from their nests. Unlike the House Sparrow and European Starling, House Wrens are federally protected. You may not remove nesting material, eggs, nestlings, or adult House Wrens from a nest box. If House Wrens are not wanted, wait until after the breeding season is over to move the nest boxes away from bushy areas, which are prime House Wren habitat. Another solution is to place a box or two in wren habitat. This gives wrens a place to nest and decrease the chance that they will move to other habitats and usurp boxes from others species.

Wasps and Bees

Seldom do wasps and bees usurp boxes from nesting birds. They are mostly found in empty boxes. If these insects are found in a box, it is best to let them be and not take any active measures to exterminate them. Instead, wait to clean them out in the fall when the weather is cooler and their activity is halted. You can prevent wasps and bees from establishing themselves by applying a thin layer of soap (use bar soap) onto the inside surface of the roof. This will create a slippery surface between the insects and the roof of the box.

European Paper-wasp

The European Paper-wasp (Polistes dominulus), introduced to North America in 1980, is quickly increasing its range along the eastern United States.

The European Paper-wasp is colored black and yellow like a yellow jacket and is slightly smaller than our native brown and tan Common Paper-wasp (Polistes fuscatus). The wasp prefers to nest in cavities such as nest boxes and it attacks people with much less provocation than the native paper-wasp. Unlike the common wasp, the European Paper-wasps, often uses the same nest year after year, resulting in early nesting and larger nests.

Mice

Mice are usually problematic when they begin to build their nests for the winter. Because this happens after the birds are finished breeding, most nest box monitors do not evict mice, but allow them to nest in their boxes throughout the winter. These boxes need to be cleaned out in early spring, however, or birds will not use the boxes.