They sing and chip and look cute as a button. But when they gather in flocks, they become truly annoying and very costly pests. Yes, some birds can be a real nuisance. And after you've tried waving your arms, shouting, using water hoses and everything short of black magic, there comes a time when you say to yourself, "I need the kind of bird repellent the pros use."

Whether you're a homeowner, boat owner or a facilities or city manager, you probably know the damage pest birds can cause. Their poop can discolor paint, ruin wood, and eventually turn metal into something resembling cardboard. They can turn a fine stone statue into a façade that looks more like a coral reef. Even worse, bird deposits can carry and transmit any of 60 known diseases. The point is, pest birds create millions of dollars of damage every year. So the sooner you keep them away from your property, the better.

Lucky for you, people have made it their life's work to learn what pest birds hate. Better still, you can avail yourself of the many products borne out of this research--bird repellants that are humane, inexpensive and easy to install. Bird repellents that work.

If you're troubled by flocks of pigeons and other large birds, the Bird Spike can be your best friend. These repellents are basically strips of spikes made of rigid unbreakable polycarbonate, perfect for discouraging pest birds from landing on rooftops, signs and other elevated areas and building tops. In some cases, where conductivity or radio interference is not an issue, flexible stainless steel spikes are available.

For flat surfaces, awnings and patio covers, there's the Bird Spider. The spider arms wiggle and wave in the breeze, so birds will simply look for another place to land. Spiders come in various diameters to discourage all manner of bird sizes. They're basically maintenance free and harmless to birds.

If you're looking for something really simple, but surprisingly effective, you might try the now famous Bird Repellent Slope. They're more slippery than wet pigeon poop and birds who try to land just slip off like a pat of butter on a hot ear of corn. Made of PVC panels, bird slopes are easy to install and perfect for eaves, ledges, beams and other 90-degree crannies where pest birds like to nest and roost.

If you're into chemical bird repellents, there's bird gel. This relatively simple solution is easily applied with a caulking gun. Once the gel dries, it skins over but never quite sets to full harness. It just leaves a sticky membrane that birds hate to land on; yet it’s safe for birds (except swallows). Bird gels can be used on any flat or curved surface, including conduit, pipes, ledges, I-beams and parapet walls.

For larger areas like warehouses, airplane hangars, courtyards, canopies, and rooftops, you might consider Bird Netting. Net mesh sizes are available to repel a number of pest bird types, including sparrows, starlings, pigeons, seagulls and bigger birds. Some brands of heavy-duty bird netting are even recommended by architects. When selecting netting for your particular application, look for products that are flame resistant, U.V. stabilized, and rot and waterproof. For most applications, try to get non-conductive netting.

Speaking of conducting, the next category of bird repellants takes full advantage of a bird's aversion to electric shocks. Known as Electric Track Bird Repellants, these convey a mild electric shock that’s harmless to birds. Easily mounted on signs, ledges, rooftops, and flat or curved surfaces, electric tracks are ideal for pigeons, seagulls and larger birds. Some low profile electric tracks are virtually invisible from ground elevations; others come in a flow-through design to prevent water from damming up on rooftops and other surfaces.

If you're convinced that birds only respond to motion, there's a whole family of motorized whirly-gigs with rotating arms to shoo pest birds away. These are well suited for parapet walls, roofs, signs, billboards, or any flat surface. Some have batteries, others you plug in, and some are solar powered.

If you're on a budget, and need something fast and economical, you can't beat the growing number of Bird Scare products that are on the market. These flashy, animated objects and banners use bird psychology to deter birds from landing. The simplest scare products use iridescent reflective foil and shiny tape waving in the breeze to create an “Optical Distraction Zone.” To really zone out a feathered pest, there's the inflatable balloon covered with lifelike reflective predator eyes. Birds think they're giant predators and won't land near them. All these scare-eye diverters are easily mounted in high, bird-traffic areas. Some bird repellants that fall into this category have iridescent eyes to scare pests by day and glow-in-the-dark reverse sides to discourage birds at night. Bird scare products are perfect for vineyards, pool areas, trees, overhangs, gazebos, boats and other open areas.

We all have sounds we hate--fingernails on a chalkboard, forks on an aluminum pan, our mother-in-law's complaints. Well, that’s what our next category of bird repellants sounds like to a pest bird. They're called Audio Bird Repellents and they emit ultrasonic sounds that drive pest birds up the wall. Ideal for enclosed areas like parking garages and overhangs, they work well anywhere pigeons, sparrows, starlings, or seagulls and larger birds gather and nest.

If you need a bird repellent for large open areas, try Foggers and Misters. These systems disperse a food-grade, non-lethal aerosol of methyl anthranilate. Approved by the EPA, this chemical makes pest birds really uncomfortable. Some systems feature multiple remote spray units that can deter pest birds for up to one square mile.