Sunday, 6 March 2011

Sailing by

Credit to Morg who reminded me it's worth looking for "sailed" Eiders, this was the second bird I looked at on arrival at my patch at Wrecked Craigs, Port Seton. Though the sail has been identified by some (Garner et al.) as the key feature of the northern race (borealis) this individual seemed to lack any obvious difference in bill/leg colour, not to mention the shape of the lobes and processes (nothing to do with the ears!).

There are various articles out there on this "race" (Ireland, Shetland) but the most interesting I have seen is the note by Gibbins & Maggs in NESBR 08* describing "sailed" birds on the Ythan, which have been proven to include a bird ringed as a chick there in mid-1980's and a recent breeding adult female. The remarkable observation of two populations ("sedentary" and "migrant") breeding adjacent to each other at same site (Milne & Robertson, 1965**) may be purely coincidental but with resident breeders displaying sails there is clearly much we still need to learn about the status and distribution of borealis Eider, and more genetic work has been called for.

Having re-read the Garner article it seems the greener bill is not inconsistent with borealis, this being a clinal feature and more typical for birds from Iceland or Svalbard, contra the orangey colour of the New World birds.

Previous observations have been made in Lothian in 2007, also in spring, with drakes at Scoughall on 18 Feb & 29 Apr, and at Aberlady on 1 Apr (I believe with BBRC). We have also had a decent number of Eider in the Forth recently with 2k+ off Gullane, given this was the second bird I looked at (out of 10 drakes total) there are no doubt more out there and we need to be looking more carefully!

* Gibbins C & Maggs H (2009) "The intriguing case of North East Scotland's sailed Eider", North East Scotland Bird Report 2008, pp. 108-110
** Milne H & Robertson FW (1965) "Polymorphisms in egg albumen protein and behavior in the eider duck", Nature 205:367

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