Monitoring Habitat Use by Male Mute Swans in the Chesapeake Bay

We tracked male mute swans (Cygnus olor) (n = 2) in 2002 and in 2003 (n = 3) using Global Positioning System (GPS) in a 217,500-ha area of the Chesapeake Bay in Maryland. We quantified habitat use among four habitat categories (submerged aquatic vegetation, open water, shoreline, and upland) and between diurnal and nocturnal periods. Swans did not use habitats in proportion to their availability; they consistently used upland less often than what was available within their home ranges. Most use occurred within submerged aquatic vegetation (SAV) and open water, which typically were the most abundant habitat types. When SAV was used, most locations were within sparse to moderately dense vegetation (11%-70% horizontal coverage). Diurnal and nocturnal use of habitats was similar. Although the sample size in our study was small, we believe this information is representative of the mute swan population in Chesapeake Bay because ground observations confirmed GPS-marked individuals always were within flocks ranging from 30-400 individuals. Given that mute swans were found in SAV frequently and are known to feed on it, they may negatively impact SAV coverage in the Chesapeake Bay. Control of mute swans in the Chesapeake Bay may be considered a viable conservation strategy for SAV restoration.

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