Nothing you can spray or hang, going by the research. No retrieved source names a smell, a sound or a taste that pigeons reliably avoid, so the honest answer here is a shrug. Most pigeon deterrents get sold to you on the promise that the bird will be annoyed into leaving. What the sources back is exclusion, the plain work of sealing openings and covering ledges so there is nowhere left to land. Your pigeon control starts with a tape measure and 1/4 inch (6 mm) wire mesh.
Watch your roof for a week and the pattern shows up fast. The same birds drop onto the same ledge and slip into the same vent, morning after morning, because that spot gives them a flat surface out of the wind. They are not being stubborn. The site works for them. So the fix that holds is the one that takes the ledge away, not the one meant to make a bird uncomfortable while it sits there. Close the vent and there is nothing to come back to.
Scare devices are the weakest thing on the shelf. Some birds adapt and become habituated to methods that alarmed them at first. The plastic owl that clears your parapet at first ends up a perch. Spikes carry a different flaw. Spikes and porcupine wire fail against smaller birds, which fit between the points and nest in the sheltered space you built for them. Pay real money for a strip of steel and you can hand a house sparrow a better nest box.
The exclusion work is specified down to the size. The Internet Center for Wildlife Damage Management calls for blocking your building openings outright. Use wood, metal, glass, masonry, plastic netting, or 1/4 inch (6 mm) rustproofed wire mesh. That covers your lofts, steeples, vents and eaves. The quarter inch is the size named for wire, and it is the part to get right. Rustproofed matters as well, because the mesh lives outdoors in the weather. To stop pigeons roosting on a building, this step does the most work, and it is the one you skip, because it means a ladder and a drill.
Ornamental architecture is the other half of your job. Cornices, column tops and carved stonework can be screened with 1 inch (2.5 cm) mesh polypropylene netting. Ask for the UV stabilized kind, so sun does not turn it brittle in a season or two. That one measure covers roosting, loafing and nesting. Pigeon netting works because it asks nothing of the bird. It closes the space. Fit it tight against the structure so you leave no gap along the edges or at the corners.
Think about your budget in those terms. Money you spend on pigeon deterrents buys you the time it takes the birds to settle in around them. Money you spend on mesh buys you an opening that stays shut. So sort your building into two piles before you buy a thing. Openings go in the first pile and flat decorative surfaces go in the second, and each pile has a material of its own.
Two things before you start. Old nesting material calls for gloves, because nest mites and lice ride along in it. The legal side is odd here as well. Pigeons sit outside state and federal bird protection, and only house sparrows and European starlings share that status. That still does not make a nest yours to judge, so check with the U.S. Fish and Wildlife Service or call a licensed professional before you work near one. Seal the building openings first. Screen the decorative stonework second. Then you can leave the pigeon deterrents on the shelf.
Read the full article: Bird Netting That Works Without Trapping
