As far as some birds are concerned, your outdoor light fixture could look like the perfect place for a nest. The fixture may have a canopy that is warm and sheltered, and it's probably mounted on a pole or attached to the house siding or the porch ceiling, making it a safe haven from ground-based predators. It's important to discourage birds early, though, because once they establish a nest, it may be illegal to disturb it. Exclude them with bird netting or deter them with visual and sonic disturbances.
Most light fixtures provide only a small space for a bird's nest, but depending on where you live, there are bound to be species small enough to take advantage of it, including swifts, martins, swallows, sparrows and starlings. In addition, Eastern phoebes, American robins and house finches are particularly fond of nesting in light fixtures.
Don't Wait for Nests
In most cases, you can't disturb a bird's nest once it's established -- the Migratory Bird Treaty Act protects migratory species at the federal level, and many states -- including Massachusetts -- extend that protection to all native species. Sparrows and starlings, which were introduced from Europe, may not enjoy government protection, but you probably don't want to remove an active nest and irreparably damage the young birds in it. Although it's legal to remove any bird nest when it's in the process of being built, it's more humane -- not to mention safer and more hygienic -- to prevent the birds from nesting in the first place.
Using Bird Netting
Many light fixtures are designed to look like birdhouses, so you can't blame birds for being attracted to them. To keep birds out while ensuring the fixture still provides the light you need, cover all openings larger than about 1 inch wide with polyethylene or polypropylene bird netting. If you can, remove the cover from the fixture and glue the netting to the inside, using epoxy resin glue, which won't degrade with the weather. If you can't remove the cover, glue the netting to the outside of the fixture.
Other strategies and devices can prevent birds from being interested in your light fixture in the first place:
- Create visual activity by hanging foil streamers or flash tape near the fixture. The activity makes birds believe predators are nearby. Hanging a mobile from a nearby tree or using a solar-powered bird-repelling fan will have the same effect.
- Put bird gel around the base of the fixture. This nontoxic substance that you apply with a caulking gun remains sticky and discourages birds from landing.
- Repel birds with sonic devices that mimic the distress calls of some species and the calls of bird predators. A low-tech approach that is more pleasant for you and which may be just as successful is to hang wind chimes from a nearby tree or overhang.