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.

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453 V o l u m e 6 8 ( 2 0 1 5 ) • N u m b e r 4 commoN scoter iN North america information on Common/Black Scoters be- tween 1944 and 2010 does not always make unambiguous reference to the subspecies involved in records, and indeed even recent databases (e.g., International Breeding Con- ditions Survey on Arctic Birds [www.arctic-]) and publications treating wildlife of northeastern Russia (Pearce et al. 1998, Stishov 2004) often do not distinguish be- tween them. Because females (and many im- mature males?) of Black and Common Sco- ters appear to be virtually indistinguishable in the feld (Garner 1989, Alderfer 1992, As- tins 1992, Waring 1993), and because adult males would seem least likely to stray well south as vagrants (as is true of adult males in many sea ducks), it is plausible that female and immature male Common Scoters have occurred, without being identifed as such, in the range of Black Scoter, and vice-versa. (Careful checks of specimen collections could perhaps produce additional records of vagrants.) Common Scoter nests next to freshwater pools, lakes, and rivers in tundra from Ice- land eastward across much of northern Eur- asia. Just to the east of its range in Russia, Black Scoter is the nesting species of dark scoter. Carboneras and Kirwan (2014) indi- cate that Common Scoter nests east to the Olenyok (Olenek) River in northwestern Si- beria; Cramp and Simmons (1977) indicate that Common Scoter nests east to the lower Lena River valley (just a few kilometers to the east-northeast of the Olenyok River); and Baldassarre (2014) gives the Khatanga River, much farther to the west, as the eastern limit of breeding range. Labutin et al. (1978) col - lected two males and female Common Scoter at Lake Taptargan east of the Lena River 3 June 1977. Labutin et al. (1985) note histori- cal nesting records slightly east of the river, in tundra lakes near the village of Tiksi, and Kapitonov (1962) notes records of nesting in the lower reaches of the Dzhardzhan River, the eastern tributary of the Lena River, south of Tiksi. Ornithologists active in this part of the Sakha (Yakutia) Republic, as well as in areas to the northeast (Chukotka), have seen no Common Scoters farther east and are aware of no reports farther east (D. Solovie- va, S. Volkov, pers. comm.). Collinson et al. (2006) considered Common and Black para- patric, and indeed the most recent surveys in the Lena River delta and adjacent areas con - frm that this is a zone of "semi-sympatry" for the two species (Syroechkovsky 2011; E. Koblik, pers. comm.). Maps presented by Syroechkovsky (2011) show the breed- ing ranges of Common and Black very close Figure 5. Adult male Black Scoter, Avalon, Cape May County, New Jersey, 16 February 2014. Adult male Black Scoters are instantly recognizable by the large orange "pumpkin-like" knob at the base of the bill. Close-up photographs of adult male Black Scoters rarely capture any color in the orbital skin, unlike in adult male Common Scoters, which regularly show a neat yellowish or orange-yellow orbital ring (compare Figure 4). Note that the nail of the bill is fairly thick and decurved in Black, more so than in Common on average. The nostrils are also set farther forward in the bill than in Common (compare Figures 1-4). Photograph by George L. Armistead. Figure 6. Common Scoter, Crescent City, California, 12 February 2015. The underwing and tail are well photographed here. In the underwing, the remiges are silvery-gray with dark outer webs, the greater (and outer median) underwing coverts are gray, and the inner median and lesser underwing coverts are blackish. Among scoter species, only Black and Common show this contrast between silvery remiges and blackish coverts in the underwing. Compared to White-winged and Surf Scoters, the tail is long and graduated, with sharply pointed rectrices (less pointed in White-winged and Surf ). In subgenus Oidema, which includes only Black and Common Scoters, the tail has 16 feathers (rather than 14, as in other scoters, all in subgenus Melanitta) and is gradu- ated for over half its length (unlike in White-winged and Surf ); the tail is also proportionately longer in Common and Black, more than twice the tarsus length (less than twice in White-winged and Surf ) (Collinson et al. 2006). The dark legs and feet, occasion- ally observed when the bird was landing or scratching, sometimes showed a ruddy cast in direct light. Photograph by Bill Kieser.

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