Debate on mute swans grows
It is no surprise that the Department of Environmental Conservation's recently unveiled plan to gradually eradicate New York's estimated 2,200 mute swans raised some public outcry. Swans easily fit into the category of "charismatic megafauna" that inspire strong emotion in people, emotions likely expressed in many of the nearly 50,000 comments and/or petition signatures the DEC received during the comment period earlier this year (the DEC is reviewing those comments and will release a revised draft, also to be open for public comment).
But also telling is that most birders heartily support the elimination plan (which still allows for managed private ownership of swans). Most people don't realize that the mute swan, that classic, graceful fixture of city parks, is invasive, an ornamental species gone wild, brought over from Europe in the late 1800s.
The Hudson Valley was ground zero, with 216 birds released in Rhinebeck in 1910, according to the DEC report that informs the proposed management plan. Mute swans eventually established breeding populations across the Hudson Valley and Long Island, down the Atlantic seaboard and around the Great Lakes.
Compared to other ornithological mistakes imported from Europe — the ubiquitous European starling and house sparrow — the swan has a limited range and small population. So, why all the fuss?
Nesting swans are quite territorial and aggressive. They may attack other birds (not to mention people or their watercraft), but more likely, they simply deter other birds from good habitat in the first place. The DEC report cites a colony of nesting birds in the Chesapeake Bay that was abandoned due to the presence of a swan flock numbering near 1,000. At a marsh in Michigan, black tern numbers dropped when swan numbers skyrocketed during the '80s. The same trend may be affecting black terns that breed upstate near Lake Ontario. They've declined since swans took hold in the '90s.
The DEC also examined swans' impact on submerged aquatic vegetation, of which they consume four to eight pounds daily. Areas the swans gorged in had 70-80 percent less vegetation than the "exclosures," which kept the swans out. This vegetation, such as the declining eelgrass beds in Long Island, provides important shelter for fish and marine life, and because the swans don't migrate, they tear it up year-round. Large numbers of swans also tended to make fecal bacteria levels in the water skyrocket, often above thresholds allowable for shellfishing.
Efforts to control mute swans are not new. In 1993, DEC adopted a policy recognizing them as an undesirable species in need of control. The Atlantic Flyway Council's 2003 plan to reduce them by 80 percent, from 14,000 to 3,000 birds, was ambitious, but hardly carried out. New York hasn't even established a hunting season for the swan, a courtesy not extended to plenty of other waterfowl.
Yes, the Long Island and Hudson Valley populations are stable or even slightly declining. But surely the modest control efforts of the DEC under their 1993 policy can take some credit for that (since 2005, the DEC has taken 500 adults and cygnets, and many more eggs). Also, swans can live 20 years, and the DEC found their reproductive success rate and adult survival rate to be robust.
Of particular threat is the increasing Lake Ontario population. Interior upstate New York contains vast amounts of suitable habitat where isolated footholds of swans could become extensive breeding populations. The DEC calls for more strenuous control efforts to prevent continued damage to sensitive ecosystems and native species.
In a New York Timeseditorial, "Speaking Up for the Mute Swan," Hugh Raffles questioned the premise of condemning a "much-loved" species simply because it is invasive, saying, "If the swans indeed displace native species, there should be a debate about the criteria used to value one species over another."
He claimed that the swan, an animal endeared in European art and myth, has only begun to be perceived as a problem in recent decades, "as conservationists' preoccupation with the geographical origins of species has intensified."
But only in recent decades has the swan become a problem, when their numbers began noticeably increasing in the '70s and '80s.
Attitudes toward the mute swan do raise the ever-fascinating debate of how we allocate value to other species. (Interestingly, ecologists at Yale just released a list ranking thousands of birds by their evolutionary uniqueness, which is one way of prioritizing conservation efforts.)
That an invasive species can be beautiful and inspire admiration shouldn't be discounted. And certainly as Raffles also suggests, "native" and "invasive" can be slippery terms especially now that humans have so muddied the waters.
In an ideal world where ecosystems were uncompromised and plenty of good habitat existed for all, the mute swan would probably not pose a huge ecological threat. But with increasing stressors placed on the natural world, we sometimes must step in and remedy past mistakes. We're stuck with starlings and house sparrows, but if we can set aside aesthetics, the still-manageable range and population of the mute swan offers us that chance.
Kateri Kosek is a member of the Ralph T. Waterman Bird Club. Valley Birder is a regular feature in My Valley by birding enthusiasts.