North American Birds

VOLUME 68 NO2 2015

A Quarterly Journal of Ornithological Record Published by the American Birding Association. The mission of the journal is to provide a complete overview of the changing panorama of our continent’s birdlife.

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T h e c h a n g i n g s e a s o n s : W i n T e r o f o u r d i s c o n T e n T 179 V O L U M E 6 8 ( 2 0 1 5 ) • N U M B E R 2 (the mean over the 1961-1990 period), the twenty-fourth coldest recorded since nation- wide data began to be collected in 1948. Large areas of Saskatchewan, Manitoba, Ontario, southern and eastern Québec, and Newfoundland experienced temperatures below average, whereas Yukon and northern Northwest Territories were above average, much like Alaska. As in the adjacent United States, Canada's Great Lakes/St. Lawrence lowlands were bitterly cold, at 1.8° C below average, making for the eighth coldest winter recorded there and resulting in the eventual freezing of most of the Great Lakes, which in turn had impacts on temperatures beyond that region (Figure 1). Overall, the winter was dry in Canada, with Environment Can- ada reporting totals 9% below the long-term average, making the ffteenth driest season since 1948; southern Saskatchewan, south- western British Columbia, eastern North- west Territories, and western Nunavut were all notably drier than average. The Quick and the Dead The freezing of the Great Lakes—the world's largest group of freshwater lakes—was big news this winter: by 6 March 2014, the ice cover was measured at 92.2%, the most since March 1979, when it peaked at 94.7% (Figure 2). Many younger birders, and younger Great Lakes residents generally, had no experience of a winter in which they could, say, walk out across Lake Superior to visit the Apostle Islands ice caverns. During an average win- ter, just 30-40% ice coverage is recorded, but "ice coverage" is a very complex and variable feature to study, as the lake ice can be of dif- ferent thicknesses, move around, and melt and re-form over the course of the winter. Moreover, the different lakes have very dif- ferent "annual maximum ice concentration" profles, ranging from 94% on shallow Lake Erie to 21% on deep Lake Ontar- io; Superior is rated 80%, Huron 63%, and Michigan 33% (Assel et al. 2003). Residents (includ - ing birders) of these regions tend not to generalize about the "great lakes" but comment instead about individual lakes' attributes. The memorable spectacle of winter 2013-2014, recounted by virtually all birders who got out and explored the Great Lakes' edges, involved legions of dy- ing and dead waterbirds, mostly ducks and grebes, that tried to inhabit the shrinking patches of open water that remained in February and into March. Print, television, and online me- dia provided coverage of the pitiable birds as well, especially in the southern Great Lakes, from Chicago to Toronto to Rochester (Belke 2014, Kane 2014, Rodriguez 2014). Reha- bilitation centers received hundreds of the birds, fnding them in poor condition, most of them with too little fat to survive. Feed- ing these birds, most of which prey on live fsh and mussels, proved to be expensive for many facilities, most of which had never re- ceived such a large number of diving ducks in a short period. Of course, this is not the frst time in history such a phenomenon has been ob- served. Even 75 years ago, Trautman, Bills, and Wickliff (1939) would refer to "a con- siderable literature relative to winter losses of waterfowl and game birds in the northern United States" already available. In the more recent history of this journal, we've looked at two instances of Great Lakes freezing and mortality/exodus of waterbirds, notably in 1994, when 90.7% ice cover was measured (Kaufman 1994). And it has been twenty years—since that winter (1993-1994)—that scientists have noted 90% of Lakes Supe- rior, Michigan, Huron, and Erie covered in ice. Midway between those two winters, in 2003, we also saw extensive freezing of the Great Lakes, with Lake Superior more than 90% ice-covered, both Huron and Erie cov- ered, and the northern part of Lake Michigan frozen. Some of the apparent effects of that 2003 event were also covered in the Chang- ing Seasons essay (Brinkley 2003). In order to make educated guesses about the effects of the freezing Great Lakes on waterbirds, we need far more accurate data than the anecdotal and piecemeal informa- tion that we have. The Great Lakes have their own distinctive winter avifauna, and in recent years, the numbers and variety of waterfowl and diving birds (and gulls) have changed, as mostly milder winters and changing food resources have permitted many birds to forego or postpone move- ments to locations farther south. The almost-record ice cover in winter 2013- 2014 is rather anomalous in the overall trend: since the early 1970s, winter ice cov- erage has declined by 63% on average. Since the 1850s, frst-freeze dates have shifted later by about two weeks, on Figure 1. The winter of 2013-2014 was characterized by warmth in the West and bitter cold in much of eastern Canada, the Midwest, and the Northeast. The eventual extensive freezing of the Great Lakes exacerbated the already cold air in the East, as the of arriving cold fronts' air temperatures were not moderated by open water on the lakes, as in warmer winters. Graphic courtesy of AccuWeather.com. Figure 2. Great Lakes Annual Maximum Ice Coverage, 1973-2014. There is clear correlation between the recent (1979, 1994, 2003, 2014) fights of Red-necked Grebes south and southeast of the Great Lakes and the peak (>90%) ice coverage. Graphic courtesy of Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration.

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