How to Control Sparrows in Purple Martin Houses

One of the problems routinely confronted by those maintaining purple martin houses is keeping undesired birds out. An example is the sparrow. As purple martins are almost entirely reliant on human structures to provide them with nesting grounds, this makes them semi-reliant on people to protect those nesting grounds from intruders. After all, if a purple martin colony arrives in your area to find its nesting space occupied by sparrows, they must look around for a nook in a building or bird house to use. That might prove very difficult or impossible for them. Unfortunately, sparrows cannot be excluded from purple martin houses using a special bird hole in the same way that a starling can. The only means of dealing with sparrows is to trap them.

Step 1

Use a Spare-O-Door trap or nest box trap. These are meant to be installed into existing bird houses and have entrances that are too small for martins, ensuring only sparrows get caught. The bird goes in, and in doing so it releases the trap door behind him. The trap doors are often made in easily-noticed colors, making it obvious when the trap has been sprung and reducing the burden of inspection. For example, the owner of a purple martin house might see that the trap has been spring when there is a sheet of red covering the opening to the bird house.

Step 2

Also try using baited traps. These usually take the form of wire cages with landing-release trap doors. Sparrows fly into the trap to eat the bait, land on the trigger, and close the trap door.

Step 3

Collect the birds from the traps, one at a time, and stuff them into a plastic drum. Be careful to re-plug the drum after putting each bird in, so as to not allow any to escape. Also take care to prevent escapes when putting a new bird in.

Step 4

Euthanize the birds. Unfortunately, if you simply release the sparrows, they will continue to be a menace to the Purple Martin colony. Spray two or three shots of engine starting fluid into the drum, and then re-plug it. The fluid will knock out the sparrows in less than a minute, whereupon they will suffocate in 30 to 60 minutes.

Starter fluid contains ether, which is the main active agent. This method certain obvious advantages over the methods recommended by the American Veterinary Medical Association (AVMA). The AVMA's main recommendation is to use carbon dioxide to knock out the sparrows and then break their necks by hand, which is plainly less palatable than allowing them to suffocate while unconscious. Their alternatives involve carrying the birds to a raptor rehabilitation center, where they will be used as hawk food, or clipping their wings. Wing-clipping reduces a sparrow's aggression towards species like purple martins, but also leaves them more vulnerable to predators.

Sources: purplemartin.org/update/HSControl.pdf; purplemartin.org/forumarchives/archive/Humane.htm; wtc.ab.ca/northernskys/sparrow.htm