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

APPENDIX D: Swan-Free Areas

All mute swans will be either excluded or removed from the following areas: 

Important SAV Beds – Submerged Aquatic Vegetation (SAV) is one of the most critical living resources in Chesapeake Bay; not only do SAV beds support fish, crab, and native waterfowl populations, but they directly improve water quality through a variety of physical and chemical processes. SAV populations are already far below historic levels, primarily due to water quality degradation following increases in human population and land use changes in the Chesapeake Bay watershed. Although the consequences of the recent accidental introduction of mute swan to the Chesapeake Bay region have not been quantified, studies of mute swans in several areas of the world have shown that these birds can negatively impact SAV communities. Whether through direct consumption, interrupting reproduction, or even trampling, mute swans could potentially exert significant local pressure on SAV survival and thus on many living resources of the Bay. The continued growth and expansion of the mute swan population in the Bay is counter to the Chesapeake 2000 Agreement's Vital Habitat Protection and Restoration goals, in particular the goal to “Preserve, Protect and Restore those habitat and natural area vital to the survival and diversity of the living resources of the bay and its rivers.”

All species of SAV will receive equal protection, for all species provide physical and water quality benefits such as reducing sediment re-suspension, increasing dissolve oxygen levels, and absorbing and sequestering nutrients. For these reasons, there are clear ecological benefits to the presence of any species of SAV. Below are SAV beds that are critically important to the Bay’s living resources and have been identified by the Chesapeake Bay Program as partial fulfillment of the goals and objectives of the Chesapeake 2000 Agreement. Submerged aquatic vegetation beds to be protected from mute swans are mapped and include: 

1. SAV restoration sites 

2. Areas vegetated less than 30% of the time since 1990 to current survey 

3. SAV in areas that contain less than 25% of its historical acreage 

4. SAV beds that are declining in size 

5. SAV in the vicinity of large numbers of mute swans

6. Core SAV bed areas (areas that have the highest persistence of SAV coverage between 1984 and 2002). These sites are believed to be consistent seed and propagule source areas.