Controlling Non-natives
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Deterring Non-native Species
Passive Control
Active
Control
Controlling Pests of Purple Martins
Overview of the problem
House Sparrows and European Starlings are exotic species, both
introduced to North America in the 19th century. They are now permanent
residents found across the United States and Canada, almost always near areas of
human habitation and disturbance (cities, suburbs) or areas with a reliable food
source (near barns or granaries). Both species nest in structures ranging from
gutters and downspouts to thick shrubs and bushes, but readily take to
artificial cavities (nest boxes) when available.
They effectively outcompete native cavity-nesting birds, and are known to destroy nests and eggs and kill nestlings and adults while taking over a nest site. If you are visiting this page, it is likely you have witnessed the havoc they wreak on our native cavity-nesting species. For more reading about general House Sparrow information, please visit the links below.
Deterring House Sparrows and European Starlings
As a nest-box monitor, your goal is to provide a safe environment for local cavity-nesting species to breed. For the reasons found on the above links, we strongly encourage that you do not allow House Sparrows to breed in your nest boxes. We recommend that you deter them from nesting in your boxes, or remove them permanently from the area where you provide your nest boxes. Unfortunately, the completely sparrow-proof nest box does not exist. There are several styles that seem to deter the sparrows for a while, but ultimately the sparrows will take to the nest box. Using monofilament line on the outside of a nest box has been under much discussion lately.
Because they are a larger bird, European Starlings aren't as much a problem when it comes to competition with Eastern Bluebirds and other smaller cavity-nesting species. Simply restricting the size of the entrance hole should be enough to give the smaller birds access to the nest box and keep starlings out. If your target species are larger cavity-nesting birds, like American Kestrels, you may have to actively remove starlings from your area. For information about discouraging European Starlings, click on the links below; for information about trapping starlings, read the section below on active control.
Passive Control
Once House Sparrows have started nesting, many nest-box monitors diligently remove nesting material. The theory holds that the birds will tire of continually building a nest that is never completed and move elsewhere. While it is certainly true that the birds will eventually seek a new nesting site, a second problem arises if they find a new site in another nest box that contains an active bluebird or swallow nest. House Sparrows will usurp the nest, oftentimes killing the inhabitants of the nest box.
Another passive method involves tricking the birds into incubating eggs that will never hatch. The theory is that the adults will remain occupied with their nest and leave the native birds in your area alone. Addling (vigorously shaking the eggs), freezing, poking a pin-hole, or boiling the eggs renders them inviable, and the female will continue to incubate for longer than the usual incubation period. The drawback to this method is the same as if nesting material was removed: the birds will eventually start another brood, often in a new nesting site that may contain an active nest. While many experienced monitors agree that these passive methods are not an effective way to control the House Sparrow populations, some monitors have used passive methods successfully on their trails.
Active Control
Active control refers to removing the birds from the area. Because House Sparrows and European Starlings are exotic species, they are not protected under the Migratory Bird Treaty Act, and nest-box monitors are legally allowed to remove them. There are several methods to remove the birds from your area, and this procedure may require trapping the birds. Several different trapping methods are listed below.
- In-box Trap
- Funnel Trap
- Trio Trap
- Repeating (Elevator) Trap
Note: the most successful method to control exotic species revolves around the simple act of placing a nest box. If you have unwanted species in your area, don’t provide a box; only place your box in habitats that do not have these birds.