Denver Birds at Airports

Bird Attractants at Airports

Airports provide a wide variety of natural and human-made habitats that offer food, water, and cover. Many airports are located along migratory routes used by birds. One of the first steps in reducing bird hazards is to recognize these attractants. Usually, several attractants acting in combination are responsible for the presence of birds and their behavior at an airport.

Food
Birds require relatively large amounts of food. Most airports support an abundance and variety of foods such as seeds, berries, grass, insects, grubs, earthworms, small birds and small mammals. Seeds and berries are sought by several migratory and resident birds such as sparrows, finches, starlings, blackbirds, mourning doves, common pigeons and waterfowl. Geese are attracted to open expanses of grasses. Gulls, starlings, robins, and crows often feed on earthworms on the surface of the ground following a rain. Gulls are opportunistic feeders and frequently feed on grasshoppers and ground-nesting birds. Raptors are attracted to airports because of rodents, birds, and other small animals that harbored by tall, poorly maintained grass stands and borders.

Occasionally, food becomes available through careless waste disposal practices by restaurants and airline flight kitchens. Airport personnel have been known to feed birds during their lunch breaks. Many airports have inadequate garbage disposal systems that permit access to various food items. These are a favorite of several species of birds, especially gulls. Nearby landfills or sewage outlets may also provide food for birds and other wildlife.

Landfills are often located on or near airports because both are often built on publicly owned lands. In these circumstances, landfills contribute to bird strike hazards by providing food sources and loafing areas that attract and support thousands of gulls, starlings, pigeons, and other species. Generally, landfills are a major attraction for gulls, the most common bird involved in bird strikes. Waste paper, paper bags, and other litter blowing across the ground attract gulls, presumably because litter is mistaken for other gulls or for food. A gull that is attracted to litter decoys other gulls and encourages flocking.

Water
Birds of all types are drawn to open water for drinking, bathing, feeding, loafing, roosting, and protection. Rainy periods provide temporary water pools at many airports. Many airports have permanent bodies of water near or between runways for landscaping, flood control, or wastewater purposes. These permanent sources of water provide a variety of bird foods, including small fish, tadpoles, frogs, insect larvae, other invertebrates, and edible aquatic plants. Temporary and permanent waters, including ponds, borrow pits, sumps, swamps, and lakes, attract gulls, waterfowl, shorebirds, and marsh birds. Fresh water is especially attractive in coastal areas.

Cover
Birds need cover for resting, loafing, roosting, and nesting. Trees, brushy areas, weed patches, shrubs, and airport structures often provide suitable habitat to meet these requirements. Almost any area that is free from human disturbance may provide a suitable roosting site for one or more species of birds. Starlings, pigeons, house sparrows, and swallows often roost or nest in large numbers in airport buildings or nearby trees, shrubs, or hedges. Large concentrations of blackbirds and starlings are attracted to woody thickets for winter roosting cover. Gulls often find safety on or near runways of coastal airports when storms prevent their roosting at sea, on islands, or on coastal bays.

 

Migration

Many airports are located along traditional annual bird migration routes. Birds may suddenly appear in large flocks on or over an airport on their annual migration, even when the airport itself offers no particular attraction. Dates of migration vary by species and area. Flock size of a given species may vary widely from year to year depending on time of year, weather conditions, and many other factors.

 

Local Movements

Shorebirds, waterfowl, gulls, and other birds often make daily flights across airports from their feeding, roosting, nesting, and loafing areas. Airports near cities may experience early morning and late afternoon roosting or feeding flights of thousands of starlings.

 

Legal Status

Most bird species are protected by federal and state laws. The legal status of problem bird species at airports should be determined before control is attempted. Migratory birds are protected under the Migratory Bird Treaty Act of 1918 (16 USC 703-711), while nonmigratory species are protected under state laws. Some species are further protected by the Endangered Species Act of 1973 (Pub. Law 93-205). These laws state make it unlawful to pursue, capture, take, kill, or possess migratory birds or endangered and threatened species, except as permitted by regulations adopted by the secretary of the interior. Permits to take nonendangered migratory birds are issued only when the birds are causing, or have the potential to cause, a serious threat to public health and safety and when nonlethal methods have failed to solve the problem. A state permit also may be required to control migratory and nonmigratory birds protected by the state.

 

Damage Prevention and Control Methods

Bird strike hazards reoccur regularly at many airports and require constant attention. Before attempting to reduce bird hazards at an airport, it is important to assess the problem, identify contributing factors, and analyze the threat to aircraft and human safety. A wildlife hazard management plan should be implemented (and may be required by FAA) to make the airport unattractive to birds. Scaring or dispersing birds away from airports is usually difficult because birds are tenaciously attracted to available food, water, and cover. As long as these attractants exist, birds will be a problem.

In most situations, a wildlife biologist trained in bird hazard assessment should be selected to conduct a thorough ecological study of the airport and its vicinity. The study should determine what species of birds are involved, what attracts them, abundance and peak use periods and special hazard zones. It should also include control recommendations to reduce the frequency of bird occurrence at the airport.

 

Fun Facts

Birds have been a hazard to aircraft from the first powered flight. During the early days of aviation, when aircraft flew at slow speeds, birds had little difficulty in getting out of the way. Bird strikes were infrequent and damage was mainly confined to cracked windshields. The likelihood of the loss of aircraft and/or human lives was remote. With the development and introduction of jet aircraft, bird strikes became a serious hazard and costly problem. Faster speeds mean birds have less time to react to approaching aircraft. The force generated by bird impact with a fast-moving aircraft is tremendous. The newer turbine engines use light-weight, high-speed mechanical parts which are vulnerable to bird strike damage.

 

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ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).