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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N O R T H A M E R I C A N B I R D S 182 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 February (96%), and few birders work the lakeshores in the dead of winter there in any case. The idea of Red-necked Grebes over- wintering on Superior stretches the imagi - nation. Alan Wormington writes: "There are certainly other sources for these birds, most notably Lake Huron and [associated] Geor- gian Bay. Another source is likely Lake Mich- igan, especially considering that the species is essentially a NW/SE migrant through the overall Great Lakes system." The rather surprising and sudden surge in Red-necked Grebe records in early March 2014 in Lake Michigan, and in the interior due south and south-southeast of that lake, suggests to me that Lake Michigan was at least one source of grebes at that time of year. It seems highly unlikely that these birds were newly arrived from, say, Lake Ontario. Evidence from past fights suggests that the grebes are detected in largest numbers to the south and southeast of the Great Lakes as a whole, which squares with their migratory trajectory in the region, as noted by Alan Wormington. Certainly, the birds could have come from farther north, though Lake Supe- rior would seem a stretch. To the east, Lake Huron could well have been the source of southern Ontario's interior grebes that fell out in February (essentially none in March in that region), but the notion that num- bers of the birds would fy westward makes little sense. In Indiana, where the fight was termed "unprecedented," Ken Brock writes: "Indiana's surge of Red-necked Grebes began in early March; indeed the frst nine days of that month yielded 96 birds. Prior to 2014, the mean number of spring Red-necked Grebes reported in Indiana over the previ- ous 20 years was 3.15 per annum. That is, more than 30 times the spring twenty- year mean appeared in the frst nine days of March." He continues: "Ninety grebes (about 94%) were found in the southern half of Indiana, at least 150 miles south of Lake Michigan. This distri - bution occurred despite the availability local patches of open water on and much nearer the lake. It is diffcult to reconcile the dearth of grebes in northern Indiana, if they were escaping the ice on Lake Michigan." This is another fascinating aspect of the data. I suspect because Michigan birders were seeing individuals. He also notes the context of the grebes (in company with many other div- ing ducks concentrated by the ice), both in Ontario and well south into the Ohio River valley and beyond, where Red-necked Grebe is also rare at any season. "If the grebes were truly spring migrants, there is no rationale as to why they would be currently appearing at these southern locations," he writes, and "if the Red-necked Grebes off Hillman Marsh were truly spring migrants, then I would ex- pect to also see some Horned Grebes and Pied-billed Grebes—but there are none." Furthermore, in the case of Horned Grebe, "record-early arrivals at Point Pelee (Febru- ary 9, 10, 15, 26) all correlated to surges of warm air at the time, up to the +10° C tem- perature range (based on Windsor Histori- cal Weather Data); in other words, there has never been an early arrival of Horned Grebe at Point Pelee that was associated with cold conditions. When I formerly lived in Hamil - ton, I do recall some late February arrivals of Red-necked Grebes, but they arrived during warm spells, and at least some of the birds were in summer plumage; all of today's birds were 100% winter plumage. The pattern of spring occurrences are well described in Bob Curry's Birds of Hamilton (2006); he likewise states that spring arrivals are associated with arriving warm weather." So it seems a settled matter that Red- necked Grebes seen in winter (through early or middle March, at least) in many interior places certainly came from the Great Lakes rather than the Atlantic. But which lakes? Looking at the season's records, we see noth- ing on or near Lake Superior, not too sur- prising, as that lake was frozen by the end of picture of grebe movements becomes much more diffcult to interpret, as some birds that had dispersed southward are almost certain- ly moving back northward (a few in breed- ing plumage), and by April, more typical patterns of migration are observed, though the number seen passing through states like Indiana was described as being orders of magnitudes higher than any previous count. In 2003, the possibility that wrecked win- ter Red-necked Grebes were all exception- ally early spring migrants was raised (Day and Iliff 2003, Veit et al. 2003). After all, we see the frst signs of returning waterfowl in the northern tier of U.S. states and southern tier of Canada as early as February in some "spring" seasons, so why not the grebes? All evidence, however, suggests that northward fights of waterfowl in late winter are the re- sult of unseasonable spells of warm weath - er—not widespread record-cold or nearly record-cold conditions and ice cover. More- over, the context for the grebe records this season was massive: numbers of grebes (up to three dozen per site) were seen in small areas of open water in the lakes in company with many species of waterfowl, and often these birds appeared to be in distress or were clearly in poor health, and many were later found dead. Alan Wormington, veteran of Point Pelee, Ontario, as well as many other great bird- ing locations, dug deeply into his decades of records, looking at the timing of grebe movements and weather phenomena. He writes: "There has been considerable de- bate lately as to if all these widespread Red- necked Grebe sightings pertain to spring migrants, or wintering birds that have been frozen out of the Great Lakes. Even before this week's obser- vations at Hillman Marsh, I concluded that these birds are wintering birds that have been frozen out of their normal win - tering areas elsewhere on the Great Lakes." Alan's analysis was spurred by his observa- tion of 36 Red-necked Grebes 7 March off Hillman Marsh, on a small unfrozen section of Lake Erie where a few had been seen beginning 5 March. He notes that the frst week of March is anomalous in the his- tory of that region, where the species is relatively rare, with just 19 spring records spanning 22 March—18 May and a pre- vious high count of just three Figure 3. Male Canvasback, Avon Lake Power Plant, 16 March 2014. Photograph by Jen Brumfeld.

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