Friday, 14 May 2010

Surf's up

The adult drake Surf Scoter was found on Monday evening whilst scanning off Port Seton from the wall by the children's playground at Wrecked Craigs, on the sea off Long Craigs with a small group of Velvet Scoter (6m, f), and has been present at the same location or closer to Wrecked Craigs each morning since (to Friday). How nice to finally see it there, having been scanning the sea here for 6 years now, sometimes daily. Presumed same was seen off Ferny Ness on 12, 14, 17 and 20 April - though the current location is more than a mile WSW so would be a stretch to see it from c/p there. Had last looked on Saturday and several times since 20 April, but I may well have missed it and it has no doubt occurred here previously. Nevertheless, under the punkbirder's self-found rules can't count this bird on my Lothian/Scottish/British lists as it is a refind, under section 5 "rarities that return to a known site each year" can only be counted by the first person to locate in any season.

I had previously seen a drake off Musselburgh, where regular in May for many years, and I was curious to work out if it is likely the same bird. Having made a summary of the spring Firth of Forth records since 1989 (pdf link) I think it is quite clear that the Musselburgh drake is a "returning" individual, having been absent only in one year since 1997, and no doubt one of the birds which formerly wintered in large numbers off the Fife coast opposite, mainly at Ruddon's Point and Largo Bay. As with Gosford Bay, where counts reached a peak of 11 individuals in late 1980's (6 adult drakes) numbers have diminished more recently in Fife, with last count of 4 drakes in 2003, max 2 since. Looking at Gosford records it seems this regular Musselburgh drake quite often calls in en route back there, this being the 4th instance of that in last 6 years, assuming it now goes on to Musselburgh again [PS - now confirmed, it was back there Saturday morning, 15 May! PPS - back at Wrecked Craigs midday! PPPS - 2 drakes off Musselburgh on 17 May, so my theory goes out of the window! Perhaps the second drake to arrive is the one which was at Seton, and this may not be the long-term Musselburgh visitor, but who knows?!].

Latest date in Musselburgh has been 11 June 2006, but I don't think we know where it goes thereafter - a record from Lunan Bay, Angus for 31 May 2007 could potentially have been the same heading north; records for scoter moult flock off NE Scotland (Murcar & Blackdog) generally inconsistent with arrivals in May whilst bird still at Musselburgh. BWP mentions a bias towards mid-summer in records from northern Scandinavia: "but in Finland and Sweden most May and June (Baltic, end April and May; Lapland, summer), suggesting stragglers may migrate with Velvet Scoters M. fusca, with which they often associate. (British Ornithologists' Union 1971; Bauer and Glutz von Blotzheim 1969; Bruun 1971.)" - consistent with the late May departure from Lothian; if travelling with Velvets then interesting that this species is typically very late in departing: "return movement from early March, but spring passage later than in M. nigra and Eider Somateria mollissima, and large flocks in Danish waters until mid-May when peak passage occurs Sweden and Finland. In USSR, one of last ducks to return, reaching Tobolsk late May and Yamal mid-June (Dementiev and Gladkov 1952)"; by contrast for Common Scoter: "Return movements late February to April in Atlantic and North Sea, April–May Baltic, and northern breeding grounds re-occupied mid-May to early June"; much of this movement apparently noctural, and also overland across Denmark and throo Gulf of Finland to White Sea.

In summary, I feel it is very likely that this male Surfie has been visiting Lothian in late spring for the last 14 years, and must be at least 15 years old since was adult at first sighting. I can't find a longevity record for this species, one source says "very little is known about the lifespan", but those for closely related White-winged and Velvet Scoters are 12.0 and 15.6 yrs, respectively. So whilst we can't prove anything it's likely that this bird is thriving in the Forth and reaching a ripe old age. Would be very interesting to compare with deduced ages of other long-term returning birds, perhaps those in Sound of Harris?

Incidentally, too far offshore for photos (initially central in photo above, on sea off Long Craigs rocks visible extending out from right, c. 1km NNE of the corner of prom), but see this selection from California to appreciate the beauty of this species.

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