Mute Swans in Maryland: A Statewide Management Plan
Maryland Department of Natural Resources
Wildlife and Heritage Service
April 14, 2003

EXECUTIVE SUMMARY

This plan describes the status and impacts of mute swans in Maryland. It is a guidance document that provides direction and objectives for the Maryland Department of Natural Resources (DNR) to manage this overabundant species through 2008. The plan’s goal, objectives, and strategies will be evaluated at the end of the 5-year period.

Mute swans are an invasive, nonnative species that now inhabit the Chesapeake Bay in large numbers. The mute swan population in Maryland increased dramatically between 1986 and 1999 (Figure 1). At the rate of increase observed during this period, and absent management, the swan population may have exceeded 30,000 birds by 2010. Between 1993 and 1999, the population grew more slowly, attributed, in part, to limited population control by the DNR and Federal National Wildlife refuges. The population decreased from 3,955 in 1999 to 3,624 in 2002 (Figure 1). Egg addling and the removal of adult swans from Federal National Wildlife Refuges and authorized scientific collecting played an important role in the population change.

Adverse ecological effects are occurring as a result of this swan population and will increase if the population is allowed to grow. The mute swan population threatens the protection and restoration of SAV beds in areas of critical importance to the Bay’s living resources. Concentrations of foraging swans can severely impact submerged aquatic vegetation (SAV) beds and restoration plantings. Foraging by swans during the growing season reduces plant survival and the plant’s ability to reproduce. This large swan population reduces the availability of SAV for wintering waterfowl and other fish and wildlife populations dependent upon SAV. Large numbers of mute swans have displaced state-threatened species of colonial waterbirds (terns and skimmers) from their island nest sites. The antagonistic behavior exhibited by mute swans toward other native wetland birds can prevent native waterfowl from using traditional nesting and feeding areas. In some cases, mute swans kill other wetland bird species. Mute swans also impact humans. The display of aggressive behavior by some swan pairs instills fear into citizens, preventing them from using their shoreline property and adjacent waters.

To address these concerns, the DNR appointed a Mute Swan Task Force in 1999 to develop management recommendations. The Task Force compiled a comprehensive summary of information about mute swan ecology, population dynamics, and management that can be viewed at http://www.dnr.state.md.us/wildlife/Hunt_Trap/waterfowl/muteswans/mstfpc.html.

The cornerstone of the Mute Swan Task Force recommendations was the protection of native species and their habitats from the effects of mute swans. The Task Force recommended that the DNR establish Swan-Free Areas, areas where mute swans would be excluded or removed to protect critically important habitats and wildlife resources. The Task Force recommendations (Appendix A) were made available to the public for comment for 60-days in March 2001. The DNR Waterfowl Advisory Committee endorsed the Task Force recommendations, but further recommended a rapid reduction of the mute swan population and the elimination of State protection for the species (Appendix A). The recommendations provided by these two advisory committees, along with biological and wildlife management principles and public input, were considered in the development of the goals, strategies, and objectives contained within this management plan.

The overall management goal is to manage the mute swan population in Maryland at a level that (1) minimizes the impacts to Maryland’s native species and habitats; (2) is consistent with the objectives of the Chesapeake 2000 Agreement; and (3) minimizes conflicts with humans. To achieve this goal, the management of mute swans shall be conducted in an effective, efficient manner, consistent with accepted wildlife management practices. 

Specific management objectives to achieve this goal are as follows:

• Develop a program of public outreach that facilitates understanding of the status of the mute swan population in Maryland, its impacts on the Chesapeake Bay ecosystem, and the problems it creates for humans.

• Exclude or remove all mute swans from “Swan-Free Areas” to afford protection to habitats critical to the Bay’s Living Resources.

• Reduce the mute swan population as quickly and efficiently as possible, consistent with activities to protect, restore and enhance the Bay’s Living Resources.

• Prevent the escape and reproduction of captive mute swans.

• Reduce conflicts between mute swans and people by permitting a wide variety of effective and efficient control methods.

• Monitor the size and distribution of the mute swan population and evaluate the effectiveness of management actions.

• Conduct additional research that will increase understanding of the role of mute swans in the Chesapeake Bay ecosystem and their impacts on the Bay’s Living Resources.