The Carsington Gull- October 2012
by Richard Lowe
A possible adult ‘fuscus’ (Baltic Gull) was reported at Carsington Water, Derbyshire on 13th October and subsequently seen on following evenings in the gull roost from Sheepwash Hide. Good views and video were obtained on 15th October which seemed to confirm the identification. This was a stunning bird – small, slender, long-winged, black upperparts with a ‘mahogany’ sheen, white head with few markings, black outer primaries with no white tips, small mirror on P10 only, slim bill – a good set of features to start off with. Critical review of video at home revealed that P1 to P3 were fresh, P4 growing (just!), P5 missing and the remaining primaries appeared old. (It is important to note that this degree of scrutiny was not possible in the field – a preening or flying bird at range in a gull roost is difficult to study to get this sort of detail.) With only three fresh primaries, surely this was a good supporting feature for ‘fuscus’, which typically only replaces (if at all) the inner one or two primaries prior to suspending its moult for its autumn migration?
Well, I thought so but just to check, I e-mailed some of my Dutch friends at Gull Research.Org with this response from Mars Musse:-
About the attached images, this will not be fuscus. The complete moult has progressed far to much, with P1-3 new, a gap showing there is active mult and only a few retained outer primaries. This is more in line with intermedius.Jonsson in BW described the ‘safe zone’ as P1, at most P2 replaced and moult then suspended prior to migration.
So, its the fact that the bird appears to be in active moult that is critical here i.e. the moult has not been suspended, as it would be if it were a typical ‘fuscus’. (The moulted wing coverts forming the white ‘lines’ on the upperwing – see videograbs – may also suggest active moult?).
A bit disappointing from the identification point of view but another great learning experience. Irrespective of it being unlikely to be a ‘fuscus’ it is still a very distinctive and attractive gull but appearances can be deceptive…
Regards to all ‘gullers’, Richard Lowe (Derbyshire, England.)