North American Birds

VOLUME 68 NO4 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/605532

Contents of this Issue

Navigation

Page 19 of 123

N O R T H A M E R I C A N B I R D S 466 T h e c h a n g i n g s e a s o n s : o d d d u c k tor, perhaps a decline in prey resources, so much that many are simply unft to make their typical migratory movements? Or is this new pattern of summering a response to excellent sources of food that had not been exploited in the past? Most summer- ing Black Scoters appear to be in female- type plumage, not adult males, though some adult males are among these focks. In situations of sudden infux or unsea- sonable appearances, one looks for signs of poor health. Unfortunately, very few birders seem to keep track of mortality (and online checklist sites are set up for live birds only), and so it has been diff- cult to fnd out much information. Crewe (2014) commented on the scoters and other sea ducks summering at Cape May: "it seems most likely that these are birds that found weather conditions not con - ducive to migration at the time in spring when they would normally be heading back north and they just decided to stay further south. This idea is supported to a certain degree by the fact that pretty much all of the over-summering birds are clearly identifable by their plumage as being sec- ond-calendar year birds and thus individ- uals that would not normally breed this year anyway. There's no pressing need for them to push all the way north to Arctic breeding grounds so typically they might head north some of the way and perhaps summer off the New England coast or the 2013-2014, with hundreds, including nu- merous adult males, scattered to the south and southeast of normal wintering areas, particularly later in the winter. Black Sco- ters did not show such a dispersal pattern into the interior that winter, suggesting that fewer Blacks winter on the Great Lakes than White-wingeds. Large counts of White-winged Scoters from Michigan this summer were probably the result of the harsh winter. A count of 154 White-winged Scoters off Clam Beach, Humboldt County 24 July was mentioned in the Northern California report, but this count is by no means un- usual there. For most of the twenty-frst century, summering White-winged Sco- ters have been seen in the hundreds off northern California, according to Elias Elias, who during inshore surveys for 16 years (focused on Marbled Murrelet) found the largest numbers most consis- tently from Redwood Creek, near Orick, north to the mouth of the Klamath River near Requa. At least some of these birds were adult males, but most appeared to be "female types," according to Elias. Gary Lester notes that farther north, coastal Oregon and Washington witnessed a mas- sive die-off of White-winged Scoters (and other seabird species) in September 2009 that resulted from a bloom of Akashiwo sanguinea, which produces substances that cause seabirds' feathers to lose their waterproofng (Terry 2009). This bloom is apparently the largest ever recorded on earth. The scoters killed were identifed as being the usual post-breeding focks that arrive in late summer to feed on shellfsh and molt fight feathers (COASST 2009). Lester notes that since 2009, researchers at Clam Beach in Humboldt County have recovered just 66 dead White-winged Scoters, in addition to 74 Surf Scoters, so perhaps not enough to raise red fags yet, and there has been no evidence of red tide algal blooms in that area. The White- winged Scoters in northern California are most likely part of the post-breeding as- semblage of all three scoter species regu- larly found in summer off Oregon and Washington; most records in late spring Maritimes, but this year, Cape May will do nicely!" However, one observer in mid- June 2014 reported about 50 dead Black Scoters near Woods Hole, Massachusetts, and apparently many were found dead in South Carolina as well. Some of these South Carolina corpses (150 birds, but including some White-winged Scoters in this count) were sent to the National Wildlife Health Center in Madison, Wis- consin, where they some were found to be in emaciated condition and some suffer- ing from schistosomiasis and aspergillosis (WHISPERS 2015). It is diffcult to see this situation as positive, especially with the change in status being so drastic. In the Pacifc, no such pattern in summer- ing Black Scoters is apparent, but these birds are part of the Alaskan population, one that has been surveyed on the nesting grounds since 2004, whereas the disjunct population that nests in eastern Canada is not well studied (Bordage and Savard 2011, Savard et al. 2015). White-winged Scoter may also be a species to watch. In the Atlantic, White- wingeds also irrupted during the Razor- bill/Black Scoter fight of late 2013 and have also been found summering from southern New England to the Carolinas in numbers (mostly singles and small groups) in the summer seasons since then. This species was clearly dealt a blow by the freezing of the Great Lakes in winter Figure 2. This Eurasian Wigeon (right rear, with female Gadwall) at Bowdoin National Wildlife Refuge, Montana 14 June 2014 was most unusual in the summer season. Photograph by Stephen J. Dinsmore.

Articles in this issue

Archives of this issue

view archives of North American Birds - VOLUME 68 NO4 2015