Friday, 23 August 2013

Baltic update

As the initial excitement died down, photos were circulated to a variety of knowing souls, and it started to become clear that the simple idea of identifying a 2cy fuscus solely on advanced primary moult as suggested in the Jonsson paper might not always hold true. Bird 1 still seems to fit the bill, being at the ideal state of primary moult, all primaries replaced during last winter and now P1-2 dropped again, and importantly also showing blackish 3rd-gen scaps and coverts, and a very white head and body. The full "suite of characters" that has started to appear to be crucial.
Bird 1 - compare wings and body to the bird to the left

Birds 2 and 3 fit the bill in terms of moult, but at opposite ends of the scale. On closer inspection of videograbs, bird 2 had in fact replaced P1-8 but P9 was missing and P10 juvenile. This is a little too advanced for the other forms, but the ideal fuscus candidate shouldn't show any active moult, and so it stumbles at this hurdle. Add to that the rather-too-pale grey scaps and coverts, and messy head, and it starts to unravel a little. Bird 3 on the other hand had a fully moulted set of primaries, and had even replaced P1-2 with 3rd-gen primaries, making it way out of the range of the other forms. Surely a Baltic then? Again, the grey tones were paler than you'd like, and whilst this might be permissible in Finland, it falls short of that suite of characters needed for a provable British record.
So what are they if they're not Baltic Gulls? That's the bit that was missing from the various experts replies: they were happy to tell me they weren't fuscus, but glossed over the alternatives. Research and discussion followed, and the most likely(?) explanation is the rapidly increasing pool of hybrids that is forming on the Norwegian coast where graellsii and intermedius are moving into the gaps left as fuscus declines. Fuscoides?!
Still, one out of three ain't bad...

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