16 Jun 2011

White-winged Scoter

Josh Jones's recent correct identification of a Stenjnegeri White-winged Scoter in Ireland has raised interest in this species and its possible entry on to the British list!
Low and behold not more than 2 months later a 2nd calendar year bird of the American form deglandi was discovered lurking off the coast of Aberdeen!  The BOU taxonomic sub-committee recommended as far back as 2005 that White-winged Scoter be recognised as a separate species from Velvet Scoter - see abstract below.

Melanitta fusca is currently treated as a polytypic species with subspecies M. f. fusca (North Europe east to the River Yenisey), M. f. deglandi (Nearctic) and M. f. stejnegeri (Asia, east of the Yenisey). A morphological analysis of seaducks (Tribe Mergini) concluded that deglandi and fusca are sister taxa (Livezey 1995. Condor97: 233–255), but stejnegeri was not included in this analysis. Adult male fusca is diagnosably distinct from deglandi and stejnegeri on the basis of both bill shape and coloration, and on the shape of the nostrils (Dwight 1914. Auk31: 293–308; Proctor & Pullan 1997. Birding World10: 56–61). All age and sex classes of fusca are diagnosably distinct from deglandi and stejnegeri on the basis of the contours of feathering at the base of the bill (GarĂ°arsson 1997. Bliki18: 65–67). Although the described sample sizes are small, male fusca and deglandi are reported to differ diagnostically in tracheal structure and (presumably as a consequence of this) courtship vocalizations (Miller 1926. Am. Mus. Nov.243: 1–5; Cramp & Simmons 1977. Handbook of the Birds of Europe the Middle East and North Africa, Vol. 1). On average, the white subocular mark of adult male fusca is smaller than that of deglandi and stejnegeri (Dement’ev & Gladkov 1952. Birds of the USSR, Moscow; Dwight 1914; Proctor & Pullan 1997). On the basis of diagnostic differences in bill structure and pigmentation, and the other morphological differences described above, it is recommended that two species should be recognized:

Velvet Scoter M. fusca (monotypic)

White-winged Scoter M. deglandi (polytypic, with subspecies deglandi and stejnegeri)

Velvet Scoter is on Category A of the British List. A further decision on possible specific status for M. d. stejnegeri has been pended awaiting analysis of vocalizations for these taxa. A manuscript on species limits in scoters has been submitted and will be published in due course.

With my own plans for Wednesdayfalling into disarray a quick phone call with Pod had me ringing Zoot to cadge a spare seat in his car for the long journey north on Tuesday. Leaving at stupid O'clock in the morning, along with Gregsy La, Zoot & Pod we stopped a couple of times for a caffeine stop before arriving on site to find around 20 -30 people looking out to sea.

With a horrible heat haze things were looking a bit difficult but after what seemed hours someone relocated the bird and everyone managed to get on it. After much discussion to ensure we were indeed looking at the right bird everyone was happy and I even managed a couple of terrible record shots that do at least show the key identification features.

The more bulbous bill has a distinct step in it when seen at high mag through the 'scope but in the photo this manifests itself as a more sloping profile when compared to the Velvet Scoters it was associating with. The grey / pink tip to the bill also contrasts with the yellow tip on that of 2nd calendar year Velvets whilst it's habit of leaning forward when moving through the water made it easy to pick out once you'd got your eye in. It was also pretty distinctive in flight with the heavier bill making it appear front heavy. There was a lot of glare even with the sun behind us and my eyes were soon smarting whilst Pod applied liberal doses of suncream to his rapidly pinkening dome.

It was nice to see so many Velvet Scoter and familiarise ourselves with this prized Wirral scarcity at distance on the water rather than in flight as is the usual viewing situation. A male Surf Scoter was an added bonus! A quick trip up the road to see the long staying King Eider on the Ythan was doubly rewarding with fantastic views of terns flying backwards and forwards with fish for their young.

A great day and nice to catch up with the lads again. Many thanks to the three of them for doing all the driving whist I rested my stinging eyes behind sun glasses on the back seat.

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