North American Birds

VOLUME 69 NO2 2016

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/705084

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V O L U M E 6 9 ( 2 0 1 6 ) • N U M B E R 2 199 T H E C H A N G I N G S E A S O N S : C A R B O N C O P Y certainly did feel that way over most popu- lated regions of North America. "Winter" really kicked off in mid-Novem- ber, as the strengthened remnants of Super Typhoon Nuri surged northward into Alaska, the strongest low-pressure event ever re- corded there, with 924 mb of pressure. The arrival of Nuri produced a massive buckle in the jet stream, a ridge over the West and trough over the East, which sent cold air southward across much of the continent, from the Rockies eastward. Massive snow to- tals associated with this cold air mass left up to a meter of snow in some Great Lakes loca- tions; Denver recorded its coldest November temperature ever, -14º F on 13 November. Bird records potentially associated with the advent of Nuri were discussed in the previ- ous essay here. In the East, December was cold but not terrifyingly so, and birders were lulled into a false sense of security by the sights of linger- ing warblers from the Gulf coast states north to Ontario (Frontispiece). Even the first few days of January were tolerable. But then the bottom dropped out in the thermometers, the lingering birds vanished (=perished), and the next eight weeks reminded us, from the eastern Great Plains to the Northeast, from the Midwest to the Middle Atlantic, of the previous painful winter. Snowstorms pounded the southern Great Lakes and New England, and temperature records of many sorts were shattered. New England had its second coldest February on record. Boston broke its old seasonal snowfall record from 1995-1996 (273.3 cm) by 7.6 cm, but Eastport, Maine had 56 cm more. With so much cold air in place, the snow didn't melt, and much of it fell between late January and mid-February, the prod- uct of five distinct storms. (In the United States, these storms are now named by the Weather Channel for the sake of convenience, but we haven't yet adapted to that regime.) The west - ern (and northern) Great Lakes actually saw lower snowfall totals than av- erage, as most storm tracks were clippers, which move southeastward from western Canada and tend to hit New England the hardest, pulling moist air off the Atlantic to produce heavy snows. In mid-February, the amplitude of the jet stream became still more exaggerated, bringing bitter cold even farther south and forcing storms across the Tennessee Valley and dropping locally very high snowfall amounts in the Southeast. The West experienced just the opposite: Arizona, California, Nevada, Utah, and Washington had their warmest winter on record, while Oregon, Wyoming, and Idaho had winters in the top-three warmest (120 years of data). Across the western states, De- cember was 3º F above average; January was top-ten warm in California, Idaho, Nevada, Oregon, Utah, Washington, and Wyoming; and overall in the western United States it was the warmest February on record, with relatively little snow west of the Mississippi River except in places along the Front Range in the Rockies and in the southern Great Plains. Drought conditions remained dire in many areas, as the high ridge of the jet stream riding over the West meant that virtually no storms transited the Pacific coast, and snow- pack was paltry over large areas that desper- ately needed it, just 8% of average by the end of March in the Sierra Nevada. Normally the wettest month of the year, California's Janu- ary was its fourth driest on record. San Fran- cisco had no precipitation at all in January, for the first time in 120 years. In Arizona, the situation was different. With the visions of flooding from Norbert/Dolly in early Sep- tember 2014 still fresh in memory, passage of several storms gave Tucson its fourth wet - test January, with 6.5 cm (69 years of data). By the end of the season, most of Arizona was categorized as having only "moderate" drought, but California suffered under ex- treme/exceptional drought over most of the state, with only the far northwestern and southeastern parts of the state listed as "se- vere." The southern Great Plains (western Oklahoma, north-central Texas) continued to have extreme/exceptional drought condi- tions, as did southeastern Oregon and the western two-thirds of Nevada. Finches, thrushes, & pigeons The bird action this season was mostly in the West, where mild weather meant com- paratively easy birding and where drying reservoirs sometimes concentrated birds. The West does not have an equivalent of the "Finch Forecast" enjoyed in the East, and the West's complex topography, combined with variable and shifting regimes of drought and deluge, means that there probably never will be such a forecast. Nevertheless, one assumes that the drivers of bird irruptions—exoduses from their usual core ranges in winter—are the same in both parts of the continent, namely a combination of the results of the breeding season and the distribution of food resources. The long-term drought in the West must surely be taking its toll on food resources, including on birds that inhabit higher eleva- tions, some of which are not well known to the majority of American birders. Movements of Cassin's Finch—a species that nests over much of the North American Cordillera but has been less intensely studied than its congeners—appear to be both altitudinal and latitudinal, but its migration is not well known, and some appear not to migrate (Hahn 1996), as is true of other fringillids. Irruptions of the species vary greatly and have been difficult to describe, given the spottiness of data, more so than flights of Pur- • 2014 • • 2015 • Figure 1. Examination of the ranks the rankings of the winter temperature anomalies over North America and adjacent areas in winter 2013-2014 (left) and winter 2014-2015 (right), based on 68 winter seasons. (For meteorologists: the metric here is the 100-500 hPa Maximum Thickness.) In the 2013-2014 winter, the cold anomaly over the Great Lakes and Great Plains was in the top two in the historical record, while the warm anomalies in the Arctic, in the western North Atlantic, and in the eastern North Pacific were all the warmest on record. In winter 2014-2015, the cold anomaly is larger and more intense—the coldest on record—whereas the warm anomaly in the western North Atlantic is the second warmest on record, and the warm anomaly over Siberia is the warmest for that region on record. Note that the Arctic in the recent winter was not as warm as in the previous. Graphic from Atallah et al. (2015).

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