Now, that REALLY is a niche market! I do know pigeons can take over a town. We had them in Washington DC when I was a kid. They can and do make a big mess. Good for you, finding this area of cleaning.
My niche market is different. I publicize my love for cats, because cat people know some cleaning people dislike dealing with pet hair, kitty litter, etc. People hire me simply because I do like cats. And when they go on vacation, guess who does the kitty sitting?? Me. Works out well all around. I havent figured the numbers out, but I would guess that right now, about 80% of my regular customers have a cat or two.