Mute swans: Beautiful but bad for the Bay
The April 8 letter, "Stop killing Bay's mute swans," contains considerable misinformation, and the Montgomery Bird Club would like to address this.
First, mute swans are non-native birds and compete directly with native species including the smaller tundra swan, which winters (or used to) in large numbers on the Chesapeake. Mute swans aggressively defend winter feeding areas from these smaller birds, and it is no surprise that wintering tundra swan numbers have declined as mute swan numbers have climbed. Mute swans have also been documented destroying nests of other birds near their breeding territories, completely eliminating colonies of black skimmers and threatened least terns, as well as killing chicks of other waterfowl.
The letter implies that mute swans do not consume submerged Bay grasses (known collectively as "submerged aquatic vegetation" or "SAV"). Be assured that these birds eat a great deal of SAV! Examination of stomachs of mute swans from two regions of the Chesapeake Bay found that 70 to 100 percent of their diet consisted of these Bay grasses. What is worse, mute swans do not migrate and thus feed on Bay vegetation during its critical summer blooming/seeding period when native SAV-grazers have left for northern climes. The 3,500-plus mute swans in Maryland were estimated to consume 12 million pounds of SAV each year. Based on these numbers, the remaining 500 mute swans would eat 1.5 million pounds of vegetation per year — still a significant impact.
SAV is vital to the survival of many important Bay creatures, including blue crabs, and can clear the water of sediment and excess nutrients. For these reasons, restoration of aquatic vegetation has long been a major goal for the Chesapeake Bay. Mute swans are a major hindrance to this effort.
(Incidentally, the algae referred to in the letter, which adversely affect SAV by clouding the water, are microscopic and not consumed by swans or any other birds.)
Mute swans are, admittedly, beautiful birds but they do not belong in the Chesapeake Bay. They should be admired in local parks and other controlled environments while our struggling native species have one more threat eliminated from their lives.
For that reason the Maryland Ornithological Society and its local chapters, including the Montgomery Bird Club, have long supported efforts to control mute swan numbers and (ideally) to remove them from the Bay.
Finally, I would like to add that terming the extensive research done to document the impact of mute swans on the Bay ecosystem "junk science" is an insult to the many dedicated biologists who have been studying this problem for decades.
Gail Mackiernan, Silver Spring
The writer is conservation chair of the Montgomery Bird Club, Chapter of: Maryland Ornithological Society. Also, she was assistant director for research, University of Maryland Sea Grant Program, now retired.