Sunday, 23 July 2017

Possible Heughlin's Gull

On Saturday I found a gull at Cotesbach tip that ticked all the boxes in part one of the Altenburg Criteria (identification of first-summer Baltic Gull) but it possibly falls down because of the second part of the criteria. However, if it isn't a Baltic Gull then what is it. Structurally it seems to fit Baltic Gull. However, it seems to be a strong Heughlin's Gull candidate. Or, maybe it is a very interesting gull just outside of our current knowledge range and so should remain un-identified? One regular contributor on Facebook's WP Gull Group said if he had to chose he would go for Heughlin's Gull. I was concerned about the complete set of fresh primaries, but check this out from the core range of Heughlin's in Russia 




Since 2014, during the summer months, I have been searching through the first-summer  Lesser Black-backed Gulls at Shawell looking for fresh looking black primary feathers. I struck lucky in July 2015 when I spotted a very good contender for a first-summer Baltic Gull at the landfill site. It is still residing with the BBRC and it may well be there for a while, as it would be the first or one of the first non-ringed Baltic Gulls accepted for Britain as far as I know.

The other LBBG sub-species moult their primaries in late autumn and there have been no proven records of either L. f. graellsii or L. f.intermedius that have moulted all their primaries, especially the longest ones, during the summer months. Studies using colour rings have failed to find any second calendar-year graellsii or intermedius having moulted all their primaries by July. Whereas L. f. fuscus generally moult their primaries whilst they are on their wintering grounds and so reappear in northern Europe with a set of new primaries in many cases. 

The criteria for separating first-summer L. f. fuscus (Baltic Gull) from the other sub-species during June, July and possibly August is as follows: (1) all retrices (tail feathers), secondaries and at least eight primaries are second generation (2) the upperparts are plain dark brown, mixed with dark grey to blackish-grey adult-like feathers. In some birds, the dark brown scapulars may have acquired paler fringes due to wear, while in others a faint pat- tern on the (greater) coverts may be visible. Birds that show scapulars and/or wing-coverts with ob- vious markings (cf plate 389) or unusually pale grey adult-type feathers (cf plate 390), however, should not be considered. Full paper HERE.

Heughlin's Gull doesn't yet have a full criteria to help identify extralimital examples.




I am awaiting on comments from Western Palearctic Gulls Group on Facebook. I have discussed it Mars Muusse one of the others of 'Field identification criteria for second calendar-year Baltic Gull' and he was impressed by this gull, but felt that the upperparts were a problem. Mars felt it wise to put it on hold until such time that more is understood about heughlini. There is a possibility that it could be a hybrid between Baltic and Lesser Black-backed Gull, but if so would the hybrid moult in line with Baltic Gull/advanced Heughlin's?







Second Generation Tail Feathers (Retrices)

Open Wing Showing Second Generation Secondaries
Another View of The Second Generation Secondaries (note neat unworn white tips and edges to the secondaries)


2 comments:

  1. Really interesting Carl........

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  2. Interesting bird to say the least. But knowing that most of the Scandinavian LBBGs that come through Leicestershire originate in western Norway, and also that there are colonies containing both fuscus and intermedius breeding together, the possibility of this being an intergrade between the two must be considered as an alternative to it being anything from further east.

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