Avitrol is a product sold for the control of nuisance pigeons. It's a poison that slowly kills the bird in such a way that it exhibits lots of behavior that alarms the other pigeons. This is the intended effect. When the flock sees one (or more) of its members acting this way they leave the area. The birds take the cue that there is something amiss and fly away. The product is mixed with feed corn. It is illegal to use it where non-target birds (anything besides pigeons, starlings, or house sparrows) might eat it.
The main drawback of this product, as I see it, is that it is so obviously temporary. If pigeons live in such high densities that they need to be controlled, they will return to a place they once saw as safe, even if a peregrine falcon, poison corn, or Godzilla drove them away. It's hard for me to imagine this stuff being developed for market. How do they sell it? "Once the pigeons are away, you can do all of the things to keep away pigeons that you should have done in the first place! Although that's really expensive and difficult and you probably never will!"
Then there's the problem of making sure that only pigeons eat it. This is basically impossible. Even in the heart of the city there are occasional seed-eaters and birdfeeder birds. You may only see the pigeons, but the other birds are there. Not to mention the secondary toxicity problem--secondary poisoning is when a predator eats a poisoned prey animal and becomes poisoned. While the pigeons might be freaked out by and avoid a thrashing, dying flock-mate, a red-tailed hawk or other predator will see it as an easy meal (the best kind).
Avitrol was invented because pigeon control is difficult. On the one hand there are pigeon fanciers and feeders, people who continue to artificially support the population of feral rock pigeons. To people who maintain buildings this is the equivalent of raising rats loose in their basements, allowing them to breed and disperse into their neighbor's houses. Then there is the fact that buildings provide ideal artificial habitats for pigeons. Ledges stand in for the stone cliffs of the Mediterranean, where pigeon ancestors nest. To make buildings unattractive to pigeons requires somehow redesigning every windowsill, every flat roof, every exposed duct. Bird spikes can cost 40 dollars for every three linear feet. And if the pigeons are persistent they'll simply pile sticks and refuse on the bird spikes until the ledge is suitable again.
Artificially increasing the levels of pigeon predators is one good step--some cities provide nest boxes for peregrine falcons. Nature provides the best solutions, but is very slow. What's needed in places where pigeons are pests are fully integrated approaches, combining many different methods with monitoring and education. One thing I'm learning about pest control is that there aren't many easy solutions. But throwing poison at a problem is very tempting for people who want a quick fix. Fortunately, due to mandatory IPM standards (more on that later), throwing poison at a problem is officially discouraged in most places.
Avitrol company website.
Watchdog group's re-editing of the Avitrol label for maximum alarmism. I guess they felt that people didn't quite grasp that it's a poison.
Article about Avitrol use in Worcester, which caused me to write this. A wildlife rehabber deals with suspected secondary Avitrol poisoning and possibly affected non-target birds.