mandag den 12. november 2012

More about 'Sailed' Eiders

Several people have posted photos of Northern borealis Eiders online and as I find the subject stimulating, I try to keep track on information and gather links for future reference and comparison. Recently, new material have been posted including some beautiful individuals photographed in West Greenland by Rasmus Due Nielsen  in early April 2012, and some great photos taken by Henrik Haaning Nielsen and Søren Kristoffersen on Svalbard this summer. I would also like to highlight the photos Peter Adriaens and Leif Jonasson have taken in Iceland, and these from Svalbard and this individual in Massachusetts

There are also nice series of more or less 'Sailed' birds from sites south of the normal borealis range including photos from Scotland provided by Martin Reid and Chris Gibbins (here and here). On Birdguides and Birding the day away there are several individuals from UK and Martin Garner and Brydon Thomason have written about the subject as has Henrik Haaning Nielsen based on birds in museum collections.

In Denmark we have so far had five records in total and surprisingly all have been in 2012 indicating that ‘Sailed’ Eiders could be more regular now that we have started focusing on them then expected from the number of claims. The first in Denmark was seen in April in Hansthol Harbour (here and here); the second was in Skagen in June (unfortunately there are only online photos of this individual on Facebook: here, here, here, here and here); the third was seen near Aarhus Harbour in the beginning of October; and the fourth was seen in late October and November in Hanstholm Harbour (herehere and here) - could this be the first claim returning to the exact same site? Finally number five was seen on Læsø in November.

Whether they all five are true borealis or whether a bit of intebreeding could perhaps be clouding issues is difficult to determine with certainty. However, Henrik Haaning Nielsen has evaluated the proposed characters against individuals seen on Svalbard and online photos, and he suggests that the extension of white feathers on side of the bill could also be of importance. The character should be that on borealis the white feathers often end below the rear edge of the nostrils whereas in mollissima the white often end below the middle of the nostrils. Very exciting and certainly a character I will try to test on Danish mollissima this winter. When I scroll through the 'Sailed' Eiders from Ythan Estuary, the feather-to-nostril character seems to be highly variable, but that may not be the case within their core range, but only among individuals with mixed genes.

Whether the Hanstholm Harbour birds in the pictures below are a returning individual or a new bird is difficult to determine. However, I have the impression that it might well be the same. The small differences could be within the individual year-to-year variation. The scapular sails are slightly higher here in October and November compared to April, but that is only to be expected as such exposed feathers will become worn during winter and thus become smaller in spring.

April 2012, Hanstholm Harbour. Foto: John Kyed.

November 2012, Hanstholm Harbour. Foto: John Kyed.

November 2012, Hanstholm Harbour. Foto: John Kyed.

This individual from Bønnerup Harbour in March 2006 is interesting for several reasons. It has small white scapular sails, a rather high forehead and colour full frontal lobes. However, the white feathers stop under the middle of the nostrils and not below the rear edge as in the first national claim from Hanstholm Harbour indicating that this bird could have mixed genes.

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