June 23rd , 2011 → 10:51 pm @

“…known to kill geese, ducks, and other wetland bird species, and also to cause nest abandonment by Least Terns and Black Skimmers, both threatened species that are native to Long Island Sound, and which can still be found, in smaller and smaller numbers, on West Haven’s Sandy Point.”

The beautiful Mute Swan (Cygnus olor) that we see along our shoreline, and that some citizens like to feed (see below for information about why you shouldn’t, if you do), is actually an introduced species from the British Isles and other parts of northern Europe and north-central Asia.  Originally released in the eastern United States in the late 19th century as an ornamental bird for estates and parks, the Mute Swan, like other nonnative invasive species, has been able to thrive and multiply here; the Connecticut population has been increasing in size by about 10% per year, and is currently estimated to be about 2,000 birds.

This phenomenal growth rate can be attributed to several causes in addition to the suitable climate and habitat: most notable are the bird’s large size, aggressive behavior, and hostile territoriality, allowing it to out-compete many native birds for food and nesting sites. In fact, so aggressive and territorial are Mute Swans that they are known to kill geese, ducks, and other wetland bird species, and also to cause nest abandonment by Least Terns and Black Skimmers, both threatened species that are native to Long Island Sound, and which can still be found, in smaller and smaller numbers, on West Haven’s Sandy Point. They have also been known to attack and injure children and pets. Further ensuring the Mute Swan’s population expansion is a low predation rate and its continued protected status in Connecticut; other states, along with the federal government, have since removed mute swans from protected status, allowing hunting and removal.

The diet of this elegant and charismatic bird consists of submerged aquatic vegetation (SAV) found in water as deep as 4 feet. They eat a variety of plant species and consume about 4-8 pounds of vegetation daily, while simultaneously uprooting and dislodging three times that amount.  In fact, overgrazing by mute swans has been so dramatic that it has led to local extinction of several important aquatic plant species. The importance of SAV to the ecology and health of both freshwater and estuarine ecosystems cannot be overemphasized:  not only does SAV provide food, shelter, and nesting habitat to a variety of native fish, vertebrate and invertebrate species; it also plays a critical role in preventing erosion and filtering out sediments and pollutants.  Thus, loss of SAV caused by large flocks of feeding swans has a devastating and detrimental impact on aquatic ecosystems.

While efforts to reduce mute swan numbers often meet with public outcry, citizens can help minimize the deleterious impact of these birds by not feeding them.  For more information on the harmful effects caused by feeding of waterfowl, go to:

http://www.ct.gov/dep/lib/dep/wildlife/pdf_files/game/NoFeedWF.pdf

http://www.hardeybordercollies.com/id

Article compliments of Robert E. Marra, Ph.D.

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