Several species of birds are commonly referred to as roosting birds. Included among these are the blackbirds, starlings and grackles (see Figs. 1-4). These birds flock together during fall, winter and early spring, often forming huge roosts in urban areas. Their presence is often objectionable because of potential health, economic and nuisance problems.
These large blackbirds are characterized by long, keel-shaped tails and yellow eyes. Male grackles often appear iridescent purple. They are about the size of a small crow and are very common in Texas. Grackles are frequently seen feeding in fields, lawns, golf courses and orchards. They nest wherever there is adequate cover such as trees in parks, yards, woodlots, orchards and marshes. Grackles are omnivorous, which means they feed on a variety of plant and animal matter. Insects make up the bulk of their diet during the spring and summer months, while grain, grass seeds, pet food and fruits provide food during the fall and winter.
Damage. Individual grackles normally do not pose much of a problem; however, when they flock together and roost in trees near homes, parks or other public facilities, they can often pose a public health hazard or nuisance. Several diseases, particularly the respiratory ailment histoplasmosis, are indirectly transmissible from birds to humans. Many of these diseases are spread from the accumulation of bird droppings under the roost site. The droppings also will damage the finish on cars and kill grass and other ornamental plants. Grackles are noisy birds, often making a disturbing and obnoxious racket.
Grackles may consume or destroy farm crops such as citrus, tomatoes, watermelons, cabbage, lettuce, grain, corn, peaches, figs and cantaloupes.
Starlings are smaller than grackles (about the size of a robin) and have short, square tails. During the winter adult starlings are speckled with light dots, but they become more iridescent and less speckled during the breeding season. Juvenile starlings are a dusky, gray color.
Starlings were introduced into New York from Europe in the late 1800s and have since spread across the entire country. They are common in urban and suburban areas and nest in any suitable hole or cavity in bird houses, buildings and trees. Like grackles, starlings eat a variety of foods, but prefer seeds and fruits. They also will feed on insects during the spring and summer when insects are numerous.
Damage. Like grackles, starlings tend to congregate and roost together in flocks. Starling roosts in urban or residential areas can be a source of disease. Starlings also can cause a considerable amount of damage to gardens and orchard crops such as grapes, strawberries, apples and cherries. They are aggressive birds and often drive away desirable song birds. They may nest in bird houses intended for purple martins, woodpeckers or bluebirds.
Although both grackles and starlings may be referred to as blackbirds, this group normally includes the Red-winged Blackbird, Yellow-headed Blackbird, Brewer’s Blackbird and the Brownheaded Cowbird. Blackbirds are about the size of robins. Red-winged blackbirds have red shoulder patches on their wings, which makes them easily identifiable. As the name implies, Yellow-headed blackbirds have yellow heads. The male Brewer’s blackbird is black with a whitish eye; the female is gray with a dark eye. The Brown-headed cowbird is the smallest of the blackbirds. Male cowbirds are black with brown heads, and females are gray. Both sexes have sparrow – like bills.
Damage. Blackbirds and cowbirds also will flock together in huge roosts. The diseases and damage that they can cause are similar to those caused by grackles and starlings; therefore, their presence in urban areas is often objectionable.
Female cowbirds lay their eggs in the nests of other birds. As a result, the host bird raises the cowbird young often at the expense of their own young.
Several things can be done to discourage roosting grackles, starlings and blackbirds. It is important to begin control measures as soon as it is evident that the birds are beginning to form a roost, because it is very difficult to displace the birds after the roost has been well established.
The use of frightening devices has proved to be the most successful method of dispersing bird roosts. Persistence and proper timing are essential. The majority of the birds will arrive at the roost about an hour before sunset each day so persons involved in the activity should be in position and ready before the first birds start to arrive. Frightening methods should begin when the first birds start to arrive and continue until dark. This procedure should continue for several evenings in a row, or until all of the birds have been moved.
Most frightening devices scare the birds away with loud noises. Since most cities have ordinances against noise-making devices, check with the police department for current regulations before using them. Neighbors near the roost site also should be notified.
(Before any pyrotechnic devices are used, notify local authorities.)
Shell crackers. These devices are 12-gauge shotgun shells that contain firecrackers. When discharged, the firecrackers are launched about 200 feet into the air before they explode. The shells should be fired so that they will explode underneath or in front of the flock of birds approaching the roost. The purpose is to produce an explosion between the birds and the roost. The last few minutes before dark, when the birds are still moving, is a critical period when the most firepower is needed.
Noise Bombs / Whistle Bombs / Racket Bombs. These devices are fired from a 15mm flare pistol. Noise bombs are firecrackers that travel about 75 feet before exploding. They should be used in the same way as the shell crackers. Whistle bombs are similar to noise bombs but do not explode. In addition to their whistling sound, they produce a trail of smoke and fire which can be well seen just before dark. Racket bombs make noise in flight but do not explode.
Fireworks. Firecrackers, rockets and Roman candles also can be used for dispersing birds. The idea is to continuously harass the birds until they leave to find a more peaceful area.
Distress and alarm calls of starlings and blackbirds have been used alone and in conjunction with other frightening devices to successfully move bird roosts. These tapes are available from many sporting good stores. The calls can be played on a standard cassette tape recorder, but the use of large speakers will make the sounds more effective. The tapes should be played as the birds attempt to enter the roost and should remain on for as long as the birds are in the vicinity.
Propane exploders, air horns and other loud noise-making devices can be effective in dispersing roosting birds. Like other methods they should be used from the time the first birds arrive until dark.
Flashing lights, streams of water sprayed at the roost, hawk or owl decoys, and helium-filled balloons all have been used as frightening devices. Their effectiveness is enhanced when they are used along with auditory devices.
Thinning roost vegetation to make it less attractive to birds often produces longer lasting results than using scaring devices. When possible, thin the roost vegetation after the birds are dispersed to discourage their return.Thinning the vegetation one time, however, is not a permanent solution to the problem. A regular vegetation maintenance program must be established.
Grackles, starlings and blackbirds that are causing damage or creating a nuisance are not protected by either state or federal law and may be taken at any time. For additional information contact the nearest office of Texas Cooperative Extension–Wildlife Services.
Download a printer-friendly version of this publication: Controlling Roosting Birds in Urban Areas
Do you have a question -or- need to contact an expert?