Blackbird Roost Control
Blackbirds and starlings often establish large roosts in areas where they are objectionable because of nuisance, economic damage and potential health problems. Grackles, brown-headed cowbirds, red-winged blackbirds and starlings form the roost populations.
These birds create three major types of roost problems:
1. Summer and fall roosts in deciduous shade trees in urban and suburban areas
2. Winter roosts in conifer trees
3. Winter roosts on structures in urban areas
Lethal control methods are limited and are seldom the solution to bird roost problems. It is possible to move the offending roost population from an established site.
Summer and fall roosts. When nesting is completed, blackbirds and starlings begin forming flocks and roosts. Sometimes roosts form by late June, but most are established during July. These flocks prefer deciduous trees. The prevalence of deciduous shade trees in urban and suburban areas makes these sites attractive to roosting blackbirds. The roosts break up in late September or October and birds completely abandon deciduous tree roosts when the leaves drop. Thousands of blackbirds may occupy several blocks of suitable shade trees in summer roosts.
Because of the location of summer roosts in urban or suburban neighborhoods, some organization and planning is necessary by the community for effective dispersal of the roost using a variety of scare devices. If a summer roost has formed in the same neighborhood over the past several years, organization and planning should be done in the spring or early summer, before the birds have arrived as the birds are more easily dispersed before they become accustomed to the site.
- Persons in the neighborhood must be consulted to determine if there is agreement on the problem.
- Contact local government authorities such as city manager, police department, health department, or others to assist and to provide a point of contact for follow-up.
- Obtain needed equipment: portable record or tape player and records or tapes of blackbird distress calls; pistol launchers with whistle bombs.
- Organize personnel (usually three or more persons, depending on roost size), including public employees or other responsible adults.
- Plan activities for at least three and possibly five or more consecutive evenings.
- Begin dispersal activities about one-half hour before dark or as soon as the birds begin settling into the roost trees; continue until dark.
When the birds first arrive in the roosting area, they may perch in nearby trees and fly around without settling into the roost trees. This activity is referred to as staging and may occur for 15 to 30 minutes before the birds actually go to roost. When the birds appear to be going to roost, begin playing the distress calls (at high volume) intermittently as the birds attempt to enter and continuously when most of the birds are entering the roost. The player and distress calls should be moved to various locations within the roost every few minutes. Shooters should use the pistol launchers to fire over the tops of the roost trees. Whistle bombs fired into the incoming flocks will help turn them back. Continue using the distress calls and scare devices as long as birds are entering the roost. After dark, cease activity, as any birds remaining in their roost will not leave and the efforts are useless.
Be persistent in follow-up on successive evenings. In large roosts, or where roosts are well established, the first evening may appear unsuccessful. Scaring may have to be continued for four or five evenings until the birds abandon the area. With small roosts, or where birds are less settled in an established roost, scaring may disperse bird flocks the first night, but should be continued for several evenings to prevent flocks from returning.
Where the dispersed flocks go is unpredictable. Some may join flights of birds going to other roosts or may set up a new roost. Once birds have been moved from one site, they usually become responsive to dispersal from another site rather easily.
Removing vegetation can be effective in controlling roost populations. It is not always possible or desirable to remove all cover. Thinning can be effective. Where possible, remove all understory shrubs and brush. Remove as many canopy trees as possible. The goal should be no interlocking canopy tree branches. NOTE: Do not attempt habitat alterations in roosts that have been active for more than a year without contacting state health officials.
Winter conifer roosts. Many blackbirds migrate south, but some sizable flocks of grackles, cowbirds and starlings remain in Missouri, during the winter, especially in the southern counties. After leaf fall, these flocks assemble in conifer plantations where they are able to take advantage of the protective cover of closely spaced conifers. Roosts are formed in late fall and may persist until March the following year.
Generally these winter roosts are in the countryside where they do not create the problems associated with summer urban roosts. The number of birds may be larger than summer roosts and cover a larger area. If necessary to disperse a winter roost, the same methods and materials with more manpower than for summer roosts would be needed. Additional equipment could include automatic exploders and 12-gauge shotguns with shellcrackers which have greater range than those needed in urban roost dispersal.
Removal of part of conifer roosts by thinning may open stands sufficiently to make them unattractive to birds. Harvest of conifer stands should be considered when winter roosts cannot be managed by dispersal of birds.
Winter roosts on structures. Starlings that remain in urban areas during the winter may roost overnight on building ledges, window sills and other parts of structures where their noise may be objectionable and their droppings deface buildings. They forage on streets, vacant lots, around trash receptacles and other places where waste food is carelessly scattered. Starlings also feed at urban and suburban bird feeders.
Sanitation to remove waste food and avoidance of structural designs that encourage roosting are basic community matters to consider. Toxic controls in urban locations are inappropriate. Tactile repellents (sticky compounds) are effective on ledges, window sills and other structural parts of buildings where the materials can be applied in ribbons or strips. Birds find these sticky compounds disagreeable underfoot and seek alternative roosting sites. There are mechanical devices with projecting wires that can be installed on structural roost sites to discourage birds from landing and perching.
Distress calls and scare devices are seldom successful in dispersing starling flocks from structures.