'Sailed' Eiders with flags at half mast in Denmark

Maybe not surprisingly, but the more flocks of Eiders I scan through the more individuals I find with some degree of white scapular sails. When I began digging in to this subject I had the impression that presence of white sails was considered to be a guarantee of Arctic or Nearctic origin; however, on current knowledge there seem to be some degrees overlap in characters between borealis and mollissima including presence of white sails.

The five different individuals in this video only have rather small scapular sails and as such you could argue that they are 'Sailed' Eiders with flags at half mast. Unfortunately we do not know whether such individuals are true borealis – at least you’ll find similar individuals within borealis range; or they are migrants originating from a hybrid zone between borealis and mollissima and as such could be considered some kind of ‘subborealis’; or they are the result of a continues flow of genes from northern populations into south Scandinavian Eiders due to abmigration.

Maybe time will tell and until then I will keep searching for the full-rigged ‘Sailed’ Eider or the odd dresseri Northern Eider

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 (here, here 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.

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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.

'Sailed Eider', 3.11.2012, off Vesterø, Læsø

On November 3, 2012 I found another ‘Sailed Eider’ in Denmark. This is my third individual this year alone indicating that they are more regular than the number of records suggest. Whether they are true Northern 'borealis' Eiders or they represent intergrades between borealis and mollissima is yet undetermined. However, the characteristics of the Danish individuals are replicated within true borealis populations in the north Atlantic such as West Greenland, Northern Iceland (or are they hybrid populations?) and wintering Eiders at Svalbard.

Besides the white scapular sails several other characters indicate some degree of borealis influence, such as the head which had a high and steep forehead; the feathered white area on the side of the bill which was pointed and the black feathering below the frontal bill lobes which was very narrow; the frontal lobes on the forehead which were rather pointed and brightly coloured; and finally the white tertials which were very long and even obviously hanging down over the white rump patch.
   

According to the literature, the key features of adult male Northern Eider in relation to European Eider are:

• Two stiffer modified long scapulars creates presence of white sails on the back
• Colour on the bill base, many have orange tones over the bill base
• Legs and feet colour match the bright yellowish orange tones of the bill base
• The feathered black stripe running down the side of the bill lobe is very narrow
• The feathered white area on the side of the bill is more pointed and lack the rounded tip
• The feathered white area on the side of the bill ends below the rear edge of the nostril
• The lobes differ in shape being more pointed
• Bill shape differ structurally tending to be more elongated and drooping towards tip
• Black cap often has a straight lower edge
• Head shape tend to be squarer with steeper forehead
• Breast can be richer, deeper salmon colour
• White tertials are were very long and obviously hanging down over the white rump patch

However, one has to acknowledge that between borealis and mollissima there is a high degree of variation and overlap in these characters; thus most characters are not to be considered diagnostic, but only indicative.

Head shape was rather squarer with steep forehead

The feathered black stripe running down the side of the bill lobe was very narrow

The feathered white area on the side of the bill was rather pointed and seemed to end below the rear edge of the nostril

Note the slightly orange tones over the bill base

'Sailed Eider', 9.10.2012, off Aarhus East Harbour

Today I was searching for migrating seabird off the eastern part of Aarhus Harbour when a small group of Eiders invited for a check. Right away a 'Sailed Eider' was apparent. All the other Eiders were in their smart breeding plumage, whereas this one was yet in transitional plumage. However, the white scapular sails were very obvious when the bird was resting as seen in the photos, but just like I have seen before the white sails disappear when it started diving for food.

Other characters besides the white scapular sails indicating some degree of genetic borealis influence are the head shape with a high and steep forehead; the feathered white area on the side of the bill is more pointed and lack the rounded tip, very narrow black feathering below the frontal bill lobes; narrow and rather pointes frontal lobes on the forehead, brightly coloured frontal lobes even though the bird is still in transitional plumage; long white tertials, and bill thin subterminally and with more dropping tip than molissima.

The bird is feeding and has here and in the the two photos below been photographed between dives, thus the scapular sails are not obvious. The white scapular sails were only visible when the bird was resting just as I noted on the bird I found in Hanstholm Harbour earlier this year.

Inddeling af Ederfugle efter deres racekarakterer

Ifølge Chris Gibbins inddeler de ederfugle i Skotland i forskellige kategorier, da de både ser meget typiske borealis eksemplarer og andre mindre eksemplariske. De spekulerer i hvorvidt ægte borealis ankommer om vinteren, men i stedet for at alle trække væk igen vælger enkelte måske at yngle, hvorved intermediære typer produceres. Alternativt kan de skotske ynglefugle undtagelsesvis vise et mindre hvidt sejl. Indtil det er afklaret arbejder de med følge inddeling: type-3 er de typiske lokale molissima ynglefugle som vi også har i Danmark, type-2 er fugle, der viser et blandet sæt af karakterer, der indikerer genetisk indflydelse fra borealis uden dog helt at imødekomme de fastsatte kriterier (eksempelvis har de enten hvide sejl eller særlig udformning af hovedets bare dele, eller kraftig farvning af næbbet eller tilspidsede pandelober). Til sidst er der type-1 fuglene, der imødekommer de accepterede kriterier for borealis i kraft af stor hvide skuldersejl, orangefarvet overnæb og tilspidsede frontallober ligesom det seneste fund fra Hanstholm.

Fuglen fra Hanstholm havde markante hvide sejl, tilspidsede frontallober, smal og tilspidset sort stribe langs undersiden af loberne, et tilspidset hvidt fjerområde på siden af næbbet, mere tilspidset næb med dryppende form yderst foruden en mere stejl pande, der gav hovedet en mere kantet profil. Alene hovedets form, struktur og fjerområder gjorde fuglen til en meget påfaldende fugl, hvor de hvide skuldersejl blot bidrog til for alvor at få fuglen til at træde frem blandt de få molissima i havnen. En flot fugl, der har kick startet min interesse i emnet.

Andre har heldigvis også beskæftiget sig med emnet, hvorfor der nu ligger kommentarer og billeder forskellige steder på nettet. Se eksempelvis nogle af de billeder Peter Adriaens og Leif Jonasson har taget på Island, Martin Reid og Chris Gibbins her og her har taget i Skotland eller dem der ligger på Birdguides og her foruden dem fra Svalbard og Massachusetts. Det er også interessant at læse hvad Martin Garner og Brydon Thomason skriver om emnet.

Jeg har selv bladret mine egne billeder af ederfugle igennem, hvorved jeg fandt følgende interessante fugle i samlingen. Begge fugle er fotograferet i Bønnerup Havn den 13. marts 2006, hvor særligt mange ederfugle sås i havnen.

Fugl 1: er hvad man som minimum kan kalde en type-2 pga. de små hvide sejl, mens resten faktisk matcher borealis på flere karakterer. Bemærk således også de lange tertiærer, der hænger ned over svingfjerene, hvilket også fremhæves som en pro-borealis karakter.

Fugl 2: er også lidt interessant, da den har ret brede og afrundede frontallober, rund pande i glidende overgang til et rundet overnæb, der giver et konvekst udseende. Man kan sige, at den giver et 5-10 % dresseri Northern Eider-agtigt indtryk, hvilket blot underbygges yderligere af at det grønne på halssiden så småt strækker sig fremad under den sorte kalot. Det er naturligvis lang vej til den ægte dresseri vare, som eksempelvis måske sås i den tyske østersø i vinters (her, her, her, her, her og her). Men fuglen afspejler blot, at variationen hos de danske ederfugle er større end typisk beskrevet og er derfor ret interessant dokumentationsmæssigt. Glæd dig til vinter...

Nordatlantisk ”borealis” Ederfugl er sofakryds til de fremsynede

Søndag den 1. april 2012 fandt Jeppe Bundgaard, Peter Bundgaard, Henrik Læssøe og jeg en adult han Ederfugl med karakterer svarende til Somateria mollissima borealis fra de arktiske områder i Nordatlanten. Det er formentlig først gang formen dokumenteres i Danmark og i hvert fald første gang den kan twitches.

For dem der går op i sofakrydser er det værd at påpege, at DNA studier antyder, at Ederfugl måske vil blive udskilt i fire arter: S. v-nigrum (Pacific Eider), S. borealis (Northern Eider), S. dresseri (Canada /Amarican Eider) og S. mollissima (European Eider). "Northern" Ederfugl er langt den mest sandsynlige af de tre trækgæster og synes at forekomme årligt ud af de nordlige kyster i Storbritannien og Irland, hvorfor det er muligt og endog meget sandsynligt, at fugle har været overset i Danmark tidligere.

Afgørende for bestemmelsen af en adult han borealis i forhold til mollissima er:

• Tilstedeværelse af små hvide ”skulderblad sejl” på ryggen
• Næbbets påfaldende gule farve med et svagt orange skær særligt på ”frontallapper”
• Benene har samme farve som inderst på overnæb
• Næbbets strukturelle afvigelser med smallere og mere ”hængende” yderst halvdel
• Mere tilspidset område med hvide fjer på siden af næbbet
• Smallere og mere tilspidsende stribe med sorte fjer under de sennepsfarvede ”frontallapper”
• Sort hætte har ofte mere lige underkant under øjet
• Mere firkantet hovedform særligt med stejlere pande
• Mere kraftigt laksefarvet bryst

Hos borealis ses en glidende overgang i næbbets farve og frontallappernes form fra øst til vest, hvor fugle i øst (Svalbard og nogle i Island) har oliven-grå næb foruden tilspidsede frontallapper, mens fugle i det vestlige Grønland og nordøst Canada) har mere orange skær i de gule sennepsfarvede næb og bredere frontallapper med mere rund afslutning op mod panden. Farven på ben og fødder følgerne gerne næbbets dominerende farve, hvor fugle med kedelige olivenfarvede næb har kedelige olivenfarvede ben, mens fugle med de lyseste gule eller gulorange næb har de kraftigst gulfarvede ben og fødder.

Den er således ganske let at genkende borealis særligt pga. de små 'skulderblad sejl' og de lyse gule og svagt orange toner på næbbet. Men hvorvidt de hvide sejl er synlige afhænger af fuglens adfærd. I søndags var sejlene lagt ned under fouragering og når den svømmede op mod bølgerne, mens de pludselig blev rejst, når fuglen indtog en mere afslappet positur.

Indtil videre ser det ud til, at kun trækgæster til Vesteuropa fra længere mod nord og vest har tydelige hvide sejl, og sådanne små hvide ”skulderblad sejl” på ryggen anses i øjeblikket for at være en garanti for Arktisk eller Nearctic oprindelse. Fuglens farve på næbbet og formen af frontallapperne indsnævrer det til en oprindelse formentlig fra nordvest Atlanten.

Presumed Northern Eider (S. m. borealis), 1.4.2012, Hanstholm Havn

This ‘presumed to be’ of the form borealis also known as ‘Northern Eider’ was found feeding in Hanstholm Harbour by Jeppe Bundgaard, Peter Bundgaard, Henrik Læssøe and me on 1st April 2012. It could become the first Danish record and it feels great finally to find one with white sails following my 2009 attempt.

It was really a stunning Eider and was quite easily recognised in comparison with the two Common Eiders occasionally swimming next to it. Superficially it is very similar to the dapper black and white plumage of Common Eider but it is the small ‘scapular sails’ and also the bright yellow tones of the bill that really set them apart.

The ‘Northern’ form also known as ‘Borealis’, (which is also the Latin name Somateria mollissima borealis) is basically the name given to the subspecies in the Arctic regions of the North Atlantic, from North East Canada, Greenland, Iceland and Svalbard. There are several subspecies in the ‘Common Eider’ group; besides the Common Eiders (S. m. mollissima) there are three of which we should be (and many are) on the lookout for as they could potentially turn up as vagrants.

Livezey (1995) suggests that the Common Eider is actually four species: S. v-nigrum (Pacific Eider), S. borealis (Northern Eider), S. dresseri (Canada/American Eider) and S. mollissima (European Eider). ‘Northern’ Eider is by far the most likely target and it is possible and indeed quite likely that birds have been over looked in Denmark in the past.

According to Garner (2008), Garner & Millington (2010) and Van Duivendijk (2010) the key features of adult male Northern Eider in relation to European Eider are:

• Two stiffer modified long scapulars creates presence of white sails on the back
• Colour on the bill base, many have orange tones over the bill base
• Legs and feet colour match the bright yellowish orange tones of the bill base
• The feathered black stripe running down the side of the bill lobe is very narrow
• The feathered white area on the side of the bill is more pointed and lack the rounded tip
• The lobes differ in shape being more pointed
• Bill shape differ structurally tending to be more elongated and drooping towards tip
• Black cap often has a straight lower edge
• Head shape tend to be squarer with steeper forehead
• Breast can be richer, deeper salmon colour

The Northern Eider appears to occur annually off the northern coasts of Britain and Ireland. The origin of these birds remains uncertain but, in terms of movement and migration, birds from Canada, Greenland, and maybe Spitsbergen, could all occur within our area.

This image shows how in really good contenders for borealis Eider, the leg and feet colour should match the bright yellowish orange tones of the bill.

See this photo indication of positive borealis characters.

Nice rich yellowy bill, extra wings/nipples/spurs/sails/fins (whatever you want to call them) protruding from its back, “English Mustard” coloured legs and feet and narrow black running down the sides of the bill lobes. The lobes too differed in shape from the other “Common” Eiders, so it ticked the boxes in terms of sub ‘specific identification.

There is a cline in bill colour and frontal lobe shape from east to west, birds in east (Svalbard and some in Iceland) with olive-grey bills and fine and pointed frontal lobe, and birds in west Greenland and northeast Canada) with increasingly bright and orangey bills and slightly broader and round-ended lobe. Leg and foot colour usually mirror bill colour in that birds with dull olive bills have dull yellowy-olive legs while birds with the brightest yellow or yellow-orange bills tend to have the brightest yellow-coloured legs and feet.

All male eiders have two stiffer modified long scapulars. They are the same feathers that give male King Eider their permanently erect black sails. So far it seems that only vagrants to Western Europe from further north and west have obvious white sails and they are presently considered to be a guarantee of Arctic or Nearctic origin.

This image shows how the bill shape tends to differ structurally as well as by colour, tending to be more elongated and drooping towards tip.

The difference in bill colour to the accompanying Common Eiders is quite distinct. The shape of the lobes (the extremity of bill that runs up towards forehead) tends to be different as does the black that borders it...

References

Garner, M. 2008: Frontiers in Birding. BirdGuides Lft., Sheffield.
Garner, M. & Millington, R. 2010: The forms of Common Eider: their identification, taxonomy and vagrancy. Birding World 23(2): 65-82.
Livezey, B.C. 1995: Phylogeny and evolutionary ecology of modern seaducks (Anatidae: Mergini). Condor 97: 233-255.
Van Duivendijk, N. 2010: The Advanced Bird Guide: ID of Every Plumage of Every Western Palearctic Species. New Holland, London.