Mid-summer Mute Swan Survey Report
Atlantic Flyway Council and Technical Section
July 2000
The 1999 Mid-Summer Mute Swan Survey (MSMSS) was completed during August and September. Survey data was not collected in Canada, however, so the overall mute swan population is under counted. Canadian reports for the previous MSMSS indicated static growth. MSMSS were also conducted during 1986, 1989, 1993, and 1996. The following report provides the results of 1999's count and comparisons with the 1986-survey year (Table 1). Regional comparisons are made to emphasis the growth patterns of mute swans within the Atlantic Flyway (Table 2).
Since 1986, the Atlantic Flyway population of feral mute swans has grown 118 %, from 5,800+ birds to over 12,600 swans. This growth is seen throughout the Flyway, particularly in the Chesapeake Bay region (Maryland and Virginia) which has increased 1271.3 %. This rapid growth rate in the Chesapeake Bay exemplifies the potential growth rate that this invasive species could have throughout the Flyway.
The southern New England states of Massachusetts, Rhode Island and Connecticut had a growth rate of 43 %. Connecticut showed the lowest growth rate, 10.8 %, which does not correspond with its neighboring states (including New York). Mute swan movement, inland up major river systems and out of the survey areas may have caused this lowed count.
Although the northern New England States reported few birds, it is important to note that 13 years ago there were none (Vermont) or fewer (ME and NH) swans in this region. Maine reported a pair of mute swans with 4 cygnets on a remote lake in the north central section of the state. Possibly a pair emigrating from Quebec, Canada. New Hampshire's population remains low, with birds found primarily in the coast zone. Vermont had no swan sightings, a decrease since 1996 (11), attributed to a new mute swan management policy.
The upper Mid-Atlantic States of New York, New Jersey and Pennsylvania had a combined mute swan growth rate of 62.4 %. New Jersey showed the greatest growth with 157.8 %. Considering the amount of New Jersey's wetland acreage continued growth of this population is expected. Delaware is able to maintain a small feral population through a sound management program. Pennsylvania only had an 8 % increase. At present, however, most mute swan sightings have been in the southeast region of Pennsylvania and include mostly domestic birds on private ponds. These swans are a potential nucleus for a future feral population and a situation similar to coastal states.
During the 13-year period of surveys, the population has annually contained between 9.8 and 12% young of the year, with a period average of 11.3%. The ratio of cygnets/brood during 1999 (3.4) is similar to the 13-year average. Assuming the average clutch size for mute swans is 6.2 eggs (Willey 1968, Reese 1975, and Chasko 1986), then the average 3.3 cygnets per brood nearing flight stage indicate a possible annual first year survival rate of 53.2%.
A comparison of the Mid-Summer Mute Swan Surveys and corresponding results in the following Mid-Winter Waterfowl Surveys show similar grow rates. The MSMSS provides more accurate information on total numbers of birds and age composition of the population, however.
Prepared by:
Charles C. Allin, Pr. Wildlife Biologist
Rhode Island Department of Environmental Management
Division of Fish and Wildlife
Literature Cited
Chasko, G.C. 1986. The impact of mute swans on waterfowl and waterfowl habitat. Connecticut Dept. of Environ. Prot., Federal Aid Proj. W-49-R-12-508. Final Report.
Reese, J.G. 1975. Productivity and management of feral mute swans in the Chesapeake Bay. J. Wildl. Manage. 39:280-286.
Willey, C.H. 1968. The ecology, distribution, and abundance of the mute swan (Cygnus olor) in Rhode Island. Thesis, University of Rhode Island, Kingston, RI, USA.
Atlantic Flyway Council - Mute Swan Policy
Maryland Mute Swan Task Force Recommendations
HOW TO SUBMIT YOUR COMMENTS
Chesapeake Bay Foundation - Chesapeake 2000 Agreement
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