ssp. mandtii – and possible British records.
A trip to Svalbard normally sees observers straining their eyes for Ivory Gulls and Polar Bears, but there’s a lot more on offer. On my first day at Longyearbyen, the capital, I was enjoying the chance to photograph a few commoner Arctic species, Black Guillemot being one. I was immediately struck on reviewing the first flight images by the striking wing patterning of this individual. Had I missed something back home? Was this just an aberrant individual? Or was it a previously un-recognised plumage feature? Over the course of the next couple of weeks I made a half-hearted effort to get further in-flight shots of Black Guillemots, though the afore-mentioned distractions proved too much of a draw most of the time!
Five subspecies of Black Guilliemots are recognized in the WP, arcticus (UK, Norway, SW Sweden, Denmark, White Sea), islandicus (Iceland), faeroeensis (Faeroes), grylle (Baltic), & mandtii (Arctic E North America as far south as Newfoundland, W & E Greenland, Jan Mayen, Svalbard and through to E Siberia and N Alaska).
Very few literature sources comment on racial identification, and those that do only focus on the distinctive winter plumage of mandtii which becomes significantly whiter during winter than any of the other races. Collins fails to recognise any racial difference and even the Advanced Bird ID Guide only notes differences in the winter plumage of mandtii.
Only a single recent winter record of mandtii is known from the UK, a striking bird in Talkin Tarn, Cumbria, last year (http://solwaysandpiper.wordpress.com/2013/12/22/22nd-december-2013-bonkers-inland-black-guillemot-is-a-real-mega/). As is often the way with vagrant alcids, they appear in weird inland locations.
So back to Svalbard, and after nearly three weeks of watching Black Guillies the vast majority of individuals showed two main distinctive features; white tongues on the inner webs of the primaries, and white tips to the primary coverts, and/or the lesser primary coverts (is this the correct term?). Some birds only showed one of the features, and several birds were noted resembling arctica Black Guillemot with no additional white plumage marking.
The former feature forms a distinctive white blaze in the outer wing almost akin to skua, whilst the latter feature creates a more pointed white wing patch rather than the oval or kidney-bean shape we are used to.
I was still unsure as to whether this was a feature that I had simply overlooked in the UK or something new. A search of the Iris photo database produced 2 interesting looking birds from the UK. The first a tatty first summer (?) bird photographed by Chrys Mellor in Bridlington/off Flamborough, East Yorkshire appears to show pale tongues to the inner primaries:
Whilst the second bird from late winter in the Isle of Man appears to show two or three all white primary coverts, presumably an abnormality rather than a plumage trait:
This leaves several questions, firstly are these features indicative of mandtii Black Guillemots? If so does the Bridlington Bird constitute the first British record? Or, is the feature indicative of northern birds, islandica and arctica included? If the latter is true then, like borealis Eider, we may expect to see birds with these features more commonly in Northern Scotland. I’d be very interested to hear of other similar birds at home or abroad for comparison.