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.

Issue link: http://nab.aba.org/i/502371

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V O L U M E 6 8 ( 2 0 1 5 ) • N U M B E R 2 183 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 study of 40 waterfowl corpses produced ex- pected and disheartening results: "The easiest way to gauge the birds' health was to weigh them and compare those weights to typical weights published in the ornithological litera- ture. But even before this, just by feeling the birds' breast muscles, it was clear that they were not just skinny, but starving, emaciat- ed. Weighing them confrmed this: the dead birds' average weights were 23.4% to 46.7% below published averages. What is particu- larly distressing is that early March is the time of year when these ducks should be nearing their maximum weight, gorging themselves to ready their bodies for their arduous migra- tion back to their Arctic breeding grounds." We are now able to register our records of live birds instantly from the feld through eBird, but we still lack a way to report bird mortality in anything like a systematic way in North America. The various departments of environmental quality and/or conserva- tion, or the wildlife services, tend to become most interested in mortality events when they reach large scales, but not all agencies maintain or publish data in a consistent way annu- ally (for most, staff and budgets are far too small to do this). So we are still in the dark ages of anecdotal data, but we gradu - ally became aware—mostly in March 2014—that many thousands of waterbirds had perished (Belke 2014, Brum- feld 2014), on all three south- ern Great Lakes, from Michi- gan to Erie to Ontario. Many species were found dying or dead, mostly diving birds: Red-breasted Merganser, Long- tailed Duck, American Coot, White-winged Scoter, Greater Scaup, with smaller numbers of Common Goldeneye, Com- mon Merganser, Lesser Scaup, Canvasback, Redhead, Canada Goose, Mute Swan. The sight of birds being confned to smaller and smaller areas of open water was heart-rending; the pres- ence of numerous corpses was worse still. Brumfeld (2014) writes: "It has been one heck of a two-month struggle for even the hardiest Great Lakes wintering divers—mergansers (mostly Red-breasted), scaup, Redhead, Canvasback, scoters the continent. Could we see another fight of waterbirds southward? Much of that de- pends, one would think, on mortality lev- els in this current winter—which, among other factors, infuence the productivity of the 2014 nesting season. If the grebes were decimated in one season, another fight on >90% Great Lakes ice coverage (or, perhaps, chiefy on Lake Michigan and Lake Ontar- io?) might not be assured. During the rough winter, waterfowl biolo- gists and ornithologists took an interest in the morbidity and mortality of the waterbirds impacted by the freezing of the lakes (Fig- ures 3-5). We are fortunate to live in times in which we can read about the results of scientifc inquiries so widely and so easily. The Field Museum in Chicago set out to in - vestigate the mortality of waterfowl in south- ern Lake Michigan, where birders and orni- thologists observed hundreds of distressed and dead waterbirds (Engel 2014). A careful them in March on Lake Michigan (even fairly far north), and because many grebe species migrate nocturnally, the birds could well have departed Lake Michigan in the evening and located open water at dawn, south of In - dianapolis and nearer the Ohio River valley; they would not have put down in darkness over northern Indiana, surely. Without satellite tagging (or a fortuitous radar study, cf. Jehl 2009), it is not possible to know whether grebes hopscotch from northern lakes to southern ones as the freez- es set in; certainly, birds on the move would tend to settle in whatever areas are suitable, but we don't know much about the ice toler- ances of grebes on lakes that are gradually freezing over. Presumably, when more than 95% of a lake is frozen, the situation is not good for them. We see possibly distinct "waves" of grebes in the data, with the February movement mostly east of 82° N, the March movement showing a strong compo- nent west of that line, or due south of the western Great Lakes. Whereas most of lakes recorded their fourth- highest extent of ice (earlier records set in 1977, 1979, 1994, and 1996, depending on the lake), Lake Michigan stood out, setting a new re- cord 8 March 2014, when ice cover reached 93.3%, narrowly breaking the 1977 record (93.1%). When one gets into the beautiful meteo- rological products offered by the Canadian Ice Service and by NOAA's Great Lakes En- vironmental Research Labo- ratory (GLERL), it becomes clear how complex the lakes' ice conditions are, and we clutch at straws in trying to see a "tipping point" for exodus of waterbirds in the available data. Lake Huron reached maximum ice cover- age (96.3%) on 6 March; at about the same time, Lake Erie maxed at 96.3% as well (which ranks only eighth in the records), and Lake On- tario maxed at 61.5%. If long-term forecasts are again correct, the winter of 2014-2015 will be similar or possibly more intense in the northeastern quadrant of Figure 4. Male Redhead near Avon Lake Power Plant, Lake Erie, Ohio 16 March 2014. Photograph by Jen Brumfeld. Figure 5. Red-breasted Mergansers and other duck species, near East 9 th Street Pier, Cleveland, Ohio, 15 March 2014. Photograph by Jen Brumfeld.

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