Bird Hazards

Hazards to Birds that May be Found in Your City

Pesticides have been shown to cause rapid death and debilitating effects to birds in urban areas. A 1992 study conservatively estimated that 65 million birds die per year from pesticide poisoning or effects. Annual mortality is probably in the hundreds of millions, but deaths are very difficult to document.

Insecticides — this is the group of pesticides that injures and kills birds more than any other. People should be extremely cautious when using insecticides and should attempt to limit use of these to emergency situations only. At least 40-50 different insecticides (Organic-Phosphates and carbamate) are known to kill birds even when the label instructions and rates are followed.

Herbicides/Fungicides — these groups of pesticides are usually not considered acutely toxic to birds, but have been shown to cause endocrine and other internal system effects, which can impact reproduction and other normal functioning of birds.

Rodenticides — even though this group of pesticides is specifically used to kill rodents, they may have far-reaching effects on birds as well. Depending on how these pesticides are applied, birds may come in contact with them in at least two ways. Rodenticide baits may be improperly left out where other animals such as birds may ingest them. In addition, hawks, owls, and other predatory birds may come in contact with these pesticides by consuming poisoned rodents. The major group of rodenticides is known as anti-coagulants, which cause massive internal bleeding in rodents and in birds as well.

Cats, including both house and feral cats, are non-native predators of birds and can cause excessive mortality in local bird populations. Scientists estimate that cats kill hundreds of millions of wild birds each year and three times as many small mammals! Wildlife in the Western Hemisphere did not evolve in the presence of a small, abundant predator like the domestic cat, and thus did not develop defenses against them. Cats were introduced to North America by European immigrants only a few hundred years ago. Once caught by a cat, few birds survive, even if they appear to have escaped. Infection from the cat's teeth or claws or the stress of capture usually results in death.

Communication Towers
Some 350 species of migratory songbirds have been documented to strike communication towers (predominantly radio, television, cellular, and microwave), killing an estimated four-to-five million birds per year. While we don't know what about towers attracts and kills birds and what can be done to reduce or ideally eliminate this problem, a nationwide research effort is underway. In the interim, the Service is recommending that companies proposing to site and construct communication towers follow a set of guidelines that contain the best measures presently available for avoiding fatal bird collisions. The Service believes that use of these voluntary guidelines will significantly reduce the loss of migratory birds at towers. To obtain a copy of the Service guidelines, contact the Division of Migratory Bird Management at 703-358-1714 or view it on the web at

Power lines/High voltage wires
Electric power lines and the related power equipment, especially transformers, are estimated to kill tens of thousands of birds each year, especially birds of prey. Birds are injured or die from two causes: wire strikes and electrocutions. The electric utility provider in your city can employ inexpensive bird deterrent and/or electrocution-prevention devices on the offending equipment.

Lighted Structures and Windows
A large proportion of migrating birds affected by human-built structures are songbirds, apparently because of their propensity to migrate at night, their low flight altitudes, and their tendency to be trapped and disoriented by artificial light, making them vulnerable to collisions with human-built structures and windows. These collisions result in the mortality of millions of birds each year in North America. These collisions normally occur when lights are left on in rooms or atop tall buildings at night. Even the windows in single story buildings kill birds. Lights in these buildings at night make it more difficult for songbirds to see as they fly and may actually serve as an attraction especially on foggy nights during spring and fall migrations.

According to the Fatal Light Awareness Program (FLAP), a single tall building in Chicago checked daily during spring and fall migration caused an average of 1,478 bird deaths annually, and over a period of 14 consecutive years, the cumulative kill amounted to 20,697 birds. See National Programs for more information on FLAP.

Open oil pits, industrial pits, or chemical spills
Birds can be attracted to open oil or other industrial pits and are subject to getting trapped in these pits, potentially leading to death. Oil or other petroleum products can coat bird feathers and cause major health problems to the exposed birds. In addition, chemical spills in urban areas (e.g., anti-freeze) can attract birds and can lead to their death. Anti-freeze contains ethylene or propylene glycol, chemicals that are toxic to wildlife.

Aquatic Trash
Fishing line left around ponds, creeks and rivers in urban areas can entangle birds and result in mortality. Also, "pop tops" and plastic six-pack rings from beverage cans pose debilitating hazards to migratory birds. Birds can swallow the sharp "pop tops" or become entangled in the plastic rings. Encourage recreationers to place trash in proper receptacles and enlist local volunteers to conduct regular clean-ups of these popular areas for both birds and humans.

Other Hazards
Look around: there may be other hazards to birds in the city that need attention and that are not listed here.