Thursday, November 23, 2006

Urban Long-tailed Ducks, in depth

A highlight of last weekend was the several hours we spent observing waterfowl in Toronto Harbour. Gadwalls (Anas strepera) , Mute Swans (Cygnus olor) and Red-breasted Mergansers (Mergus serrator) were among the common waterfowl we seldom observe at our inland home, about 200 km to the north. Most impressive were the rafts of Long-tailed Ducks (Clangula hyemalis) visible, and audible, throughout our visit. Some aspects of this bird's life history and charismatic presence in Toronto merit comment.
Long-tailed ducks nest as far north as the 80th parallel - the highest of the high arctic, farther north than any other waterfowl (Robertson and Savard, 2002). Many winter on the Great Lakes with a significant number in the Toronto area. While these birds are quite at home in the rough, open waters of Lake Ontario, they appear to make a very good living in the inner and outer harbours created by the Eastern Headland (Tommy Thompson Park) and Toronto Island. A summary of Christmas Bird Count data for the past 25 years reveals just how hospitable the waterfront is to these visitors from the north. Three years ago, a record high of 13,938 Long-tailed Ducks was recorded. Low counts in the 1980's and 1990's likely resulted from the freezing of near shore waters in the city. In more mild recent winters, ice has not formed on Lake Ontario.

The call of the male has been variously transcribed as ahr-ahr-ahroulit, ahang-ahóo, ow owooolee, ow ow owoolik, or unk-on-alik, take your pick. Whereas other ducks may vocalize solely during courtship or during aggressive encounters, the yodelling notes of Long-tailed Ducks seem to accompany all aspects of their highly social lives.

Click here to hear a chorus of Long-tailed Ducks (.wav file), recorded in Toronto, courtesy of the Canadian Wildlife Service.

Whether flying our feeding, courting or resting, Long-tailed Ducks vocalize continually:the song is always in season. Surely these must be among the most garrulous of animals. Beyond its volume and ubiquity, the call has always struck me as exultant - a ringing lyric with overtones as ancient as the tundra.

No less remarkable than the male's vocal repertoire is its very elegant, stream-lined appearance. George Miksch Sutton and his colleague Olin Sewall Pettingill Jr., spent the summer of 1958 documenting the breeding birds of Iceland. Long-tailed Ducks, then known in North America as Oldquaws, were common on the tundra. Sutton's comments on Long-tailed Ducks echo some of the wonder we experienced as we watched these birds foraging along the Lake Ontario shoreline.
Sewall had a wonderful experience photographing the diving Oldsquaw. Perched with his camera on the cliff edge not far from Gudrún Pálsdóttir's house, he had been able to follow the bird as it moved gracefully about, had fed on the bottom, and finally come up with big eyes sparkling and water running down its sleek plumage. I had watched many diving Oldsquaw in the American Arctic and knew how beautiful they could be.Iceland Summer (p. 93).

While Martha and I strolled along the boardwalk just west of Wards Island, we lingered to observe about 50 very animated Long-tailed Ducks that were calling and diving only a few dozen metres offshore. They dove more-or-less synchronously, each leaving the surface with a clearly audible "plop". From our slightly elevated position, we could track each bird by the bubble trail reaching the surface. After about a minute below, the birds would bob topside, many calling or chortling with apparent enthusiasm. After only a few breaths, the birds commenced their next dive.
Long-tailed Ducks swimming toward shore at Ward's Island

Long-tailed Ducks are perhaps the deepest divers of their clan. On the Great Lakes, commercial fishermen have recovered tens of thousands of drowned Long-tailed Ducks from even their deepest gill net sets, some 70 metres below the surface - a vertical descent equivalent to the height of a 23 story office building. Associated with this hyperbaric extreme, Long-tailed ducks have the greatest heart muscle mass, gram-for-gram, of any duck, goose or swan (Bethke and Thomas, 1988).

On its wintering grounds, the species is known to exploit a range of animal prey, including epibenthic crustaceans, snails and, in soft substrates, oligochaete worms. We could only speculate on the nature of today's meal. Given the shallow break of the shore and the close proximity of the birds we observed, we supposed they couldn't have been feeding at more than a few metres depth. Offshore an additional 20 metres, a pair of Surf Scoters also dove. Each would surface with a single cluster of dreissenid mussels held in the fully gaped bill. The scoter would then break up the cluster and swallow, apparently with some effort, a smaller clump of mussels.

In contrast, the Long-tailed Ducks, diving in shallower water, surfaced with nothing in their bills, suggesting that they were eating smaller, more easily manipulated prey. One possibility, given the time of year and the characteristics of the site, is that they were eating the freshly spawned eggs of Lake Herring (Coregonus artedi). While fish eggs have not yet been documented in the diet of wintering populations of Long-tailed Ducks in North America, a recent study in the Baltic Sea, off Lithuania, found that this species opportunistically exploited the "energy-rich" eggs of Baltic Herring (Clupea harengus membras) during the April spawn (Zydelis and Ruskyte, 2005).

Whillans (1979) noted that between 1880 and 1893, large numbers of gravid Lake Herring were harvested along the shore of Toronto Island. The stock disappeared over a century ago and to my knowledge, has not recovered. The return of spawning Lake Herring to these shores would certainly be noteworthy.

These highly energetic flocks of Long-tailed Ducks provide a glimpse of something truly wild - a very scarce commodity in such a built up metropolis. Against a backdrop that includes the CN Tower and completely industrialized port lands, it is deeply satisfying to note that the wild, exuberant presence of these birds is in no way diminished.

Charlie over at 10,000 Birds has compiled a stunning gallery of Long-tailed Ducks images taken on a sunny afternoon in Toronto Harbour - a must see!

Image Credits:
Photo Credits: Photo of male Long-tailed Duck (top) used with permission from Greg Newby Photography.
Christmas Bird Count graphic by Michael. Other Long-tailed Duck photos by Martha.
Bethke, R.W. and V. G. Thomas. 1988. Differences in flight and heart mass among geese, dabbling ducks, and diving ducks relative to habitat use. Canadian Journal of Zoology. 66: 2024–2028.
National Audubon Society (2006). The Christmas Bird Count Historical Results [Online]. Available at
Robertson, G. J., and J.-P. L. Savard. 2002. Long-tailed Duck (Clangula hyemalis). In The Birds of North America, No. 651 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Sutton, G.M. 1974. Iceland Summer. University of Oklahoma Press, Norman.
Whillans, T.H. 1979, Historic transformation of fish and communities in three Great Lakes Bays. Journal of Great Lakes Research 5(2):195-215.
Zydelis, R. and D. Ruskyte. 2005. Winter foraging of Long-Tailed Ducks (Clangula hyemalis) exploiting different benthic communities in the Baltic Sea. Wilson Bulletin 117(2):133-141.

No comments: