In Missouri, four species of blackbirds are common and sometimes cause damage or create a nuisance:
- The red-winged blackbird (Agelaius phoeniceus)
- The common grackle (Quiscalus quiscula)
- The brown-headed cowbird (Molothrus ater)
- The European starling (Sturnus vulgaris)
Outside of nesting season, their habit of feeding in large flocks can cause considerable damage to agricultural crops such as corn, sunflower, and sorghum. The starling also consumes cultivated fruits such as strawberries, blueberries, grapes, and cherries, and it competes with native cavity-nesting birds for nest sites. All four frequently roost at night in mixed congregations of from just a few to more than one million birds. Large roosts in trees near homes or on buildings or industrial structures can result in noise, filth, and odor. Accumulations of droppings can cause health and safety hazards, and their corrosive acidity can damage structures.
All native wildlife is protected by the provisions of the Wildlife Code of Missouri. However, the Code specifies that most damage-causing wildlife may be trapped or shot without a permit to prevent further damage. Refer to 3 CSR 10-4.130 Owner May Protect Property; Public Safety for details and restrictions. Almost all bird species are also protected by federal regulations, and special permission is needed before taking any action that harms birds, their nests, or eggs. Special permission is not needed for methods that cause no physical harm (for example, exclusion, frightening, and harassment). The European starling is not native to the U.S. and therefore is not protected by state or federal regulations. Consequently, there are few restrictions on control methods for that species.
Exclusion. Close all openings larger than one inch to exclude starlings from buildings or other structures. Heavy plastic (polyvinyl chloride, also known as PVC) or rubber strips hung in open doorways of farm buildings have been successful in excluding blackbirds, while allowing people, machinery, and livestock to pass.
Prevent roosting or nesting on building ledges by placing a wood, metal, or plexiglass cover over the ledge at a 45-degree angle. Metal protectors or porcupine wires such as Nixalite and Cat Claw can also prevent roosting on ledges, window sills, beams, and other structures.
Exclusion from agricultural crops is practical for small gardens, experimental plots, and high-value fruit crops. Use lightweight netting to cover trees, bushes, or small plots. Protect individual ears of sweet corn in garden plots by placing paper bags over them after the silk has turned brown.
Frightening/harassment. Farmers and fruitgrowers can protect crops from flocks of blackbirds with bird-scaring devices, propane exploders being the most popular item for this purpose. Shell crackers fired from a 12-gauge shotgun are also effective. Persistence is necessary when using harrassment methods. The Department wildlife damage biologist can provide information on where to obtain dispersal equipment and supplies. For methods to disperse large roosting flocks of blackbirds, see the next topic.
Bird-dispersal techniques. Blackbirds often establish three types of large roosts:
- Summer and fall roosts in deciduous trees in urban and suburban areas
- Winter roosts in conifer trees
- Winter roosts on structures in urban areas.
Lethal control methods seldom resolve roost problems and generally are not appropriate in urban areas. However, it is possible to move an offending roost from an established site.
Summer and fall roosts. When they’ve finished nesting, blackbirds begin forming large flocks and roosts, usually in July. Deciduous shade trees in urban and suburban areas make ideal roosting sites, and thousands of blackbirds may occupy several blocks of suitable trees. These roosts begin to break up in late September or October and are completely abandoned after leaf fall.
In urban locations, effective roost dispersal requires community organization and planning. If a roost was present last year, begin planning in spring or early summer before birds arrive because they are more easily moved before becoming accustomed to the site. Steps to take include:
- Consult with neighborhood residents to obtain consensus about the problem.
- Contact local officials (city manager, police and fire chief, health department, etc.) to ask for assistance and apply for any needed permits.
- Obtain necessary equipment, such as portable tape or CD player and bird distress recordings; pistol launcher(s) with whistle bombs; shell crackers; etc.
- Organize personnel (usually three or more people, depending on roost size), including public employees and/or other responsible adults.
- Plan to conduct dispersal activities for at least three, and possibly five or more, consecutive evenings.
- Begin dispersal activities about one hour before dark or as soon as birds begin settling into the roost trees and continue until dark.
When the birds first arrive, they may perch in nearby trees or fly around without settling into the roost trees. This behavior, known as staging, may occur for 15 to 30 minutes. When the birds begin going into the roost trees, you should do the following:
- Play the recorded distress calls at high volume, intermittently when the birds begin to enter and continuously when most of the birds are entering.
- Change the location of the distress caller every few minutes.
- Fire the pistol launchers over the tops of the roost trees and fire whistle bombs into the incoming flocks as they approach.
- Have fire fighters spray water into the roost trees to flush birds and further discourage roosting.
- Continue using the distress calls and scare devices as long as birds are entering the roost.
- Cease activities after dark because any birds remaining in the roost will not leave, so additional effort is wasted.
A single evening’s efforts may not prove successful for large roosts or where roosts are well established. Be persistent and continue activities for four or five consecutive evenings or until the birds abandon the area. For small roosts or where birds are less established, one night may be sufficient, but be prepared to resume activities if the flock returns.
It’s hard to predict where dispersed flocks will go. Some may join flocks of birds going to other roosts, or they may establish a new roost. Once birds have been successfully moved from one site, they are usually more responsive to dispersal efforts at another site.
Although not always desirable, thinning or removing vegetation can be effective in controlling roost populations. Remove understory shrubs and brush and as many canopy trees as possible, with the goal of having no interlocking canopy tree branches. NOTE: Contact state health officials before attempting any habitat alterations in roosts that have been active for more than one year because accumulations of feces can pose health risks.
Winter conifer roosts. Many blackbirds migrate south but some sizable flocks of grackles, cowbirds, and starlings remain in Missouri during the winter. After leaf fall these flocks assemble in conifer plantations where closely spaced conifers provide protective thermal cover. Such roosts are formed in late fall and may persist until the following March.
Generally these winter roosts are in rural areas where they do not create the problems associated with summer urban roosts, even though there may be more birds covering a larger area. If a winter roost must be moved, use the same methods and materials as with a summer roost but employ more personnel to effectively cover the larger area.
If winter roosts cannot be managed by dispersal activities, consider selective removal of some trees. Such thinning may open tree stands sufficiently to make them unattractive for roosting.
Winter roosts on structures. Starlings that remain in urban areas during winter may roost overnight on building ledges, window sills, and other features where they cause objectionable noise and deface buildings. During the day they forage in vacant lots, around trash bins, and wherever food is available.
Eliminate food sources and adopt structural designs that discourage roosting. Tactile repellents — sticky compounds that birds find disagreeable underfoot — can be applied in ribbons or strips on ledges, window sills, and other structural features. Install porcupine wire and other physical barriers to discourage roosting (see Exclusion above).
Distress calls and scare devices are seldom successful in dispersing flocks from structures.
Repellents/toxicants. Tactile repellents can be effective on buildings; see Winter roosts on structures above. Avitrol and Starlicide are slow-acting toxicants (poisons) registered for blackbird control, but you must be licensed by the Missouri Department of Agriculture to apply them. With authority from the U.S. Department of Agriculture, our Department issues Authorization to Control Wildlife forms to licensed applicators for lethal control with toxicants at specified locations.
To obtain a Pesticide Applicator License to use toxicants, contact:Missouri Department of Agriculture P.O. Box 630 Jefferson City, MO 65102-0630 Phone: 573-522-1637 Fax: 573-751-0005
To request an Authorization to Control Wildlife form, contact the Missouri Department of Conservation.
Trapping. Decoy traps can be successful in capturing limited numbers of blackbirds in some situations. Typically, such traps are large (for example, 30’L x 10’W x 6’H) and captured birds must be euthanized humanely. An Authorization to Control Wildlife form is needed to euthanize captured native blackbird species (see Repellents/Toxicants above).
Shooting. Shooting to kill with a shotgun is most effective when used occasionally to supplement or reinforce frightening methods. By itself, shooting is not cost-effective in frightening blackbirds from large agricultural fields and is totally ineffective as a means of reducing populations. To request a Shoot-To-Kill permit, contact:
USDA Animal and Plant Health Inspection Service-Wildlife Services (APHIS-WS)1714 Commerce Court, Suite C Columbia, MO 65202-1796 Phone: 573-449-3033 Toll-Free: 866-487-3297
For additional information on these and other species, visit the Internet Center for Wildlife Damage Management website listed under External Links below.