Thursday, 14 August 2014

Candles, 29th July 2014

There had been a total absence of gulls at the tip over the last couple of months, and fears of it all being over were getting serious. But the incinerator hadn't opened yet, so surely there would be some late summer gulls looking for a warm meal hereabouts?
It was a warmer afternoon than I'd have liked, but as I scrambled up the nettle-covered (under-used!) bank, I could hear gulls! There were at least 500 over the top of the tip, and they were feeding in sight - bloody marvellous. Settling down to scan through them, thoughts turned to juvenile michs: July was almost over and I hadn't seen one yet! There were plenty of juv LBBs already, and even a couple of juv Herring Gulls, and I soon picked out a couple of adult-type michs.
My mind was wandering to other potential finds, and I started to wonder when the first Casp of the autumn might turn up (assuming the tip stays open that long!), before musing that my targets tend to be different depending on where I'm gulling. It makes no sense, but in the fields at work in Lincs and East Yorkshire, I feel much more on the look out for eastern taxa, despite the fact that Telford is only c75 miles further west!

But then a bird appeared in my scope that stopped my wandering mind in its tracks. Dazzling clean white head and body, and a gleaming white underwing too, but dark upperparts ruling out any brief thoughts of a 2cy cach. As it lowered its wings, the greater coverts stood out as a moderately worn, brownish band, whilst similar lesser and especially median coverts were interspersed with newer, blacker feathers. A handful of blackish scaps stood out amongst the paler, worn mantle too, but most importantly on the closed wing, the exposed primaries looked tar black, contrasting with every other 2cy gull on the tip, which had varying numbers of worn juvenile outer primaries. The fact that this bird possessed black 2nd-generation primaries meant it had already moulted its juvenile remiges - a sure-fire feature of 2cy Baltic Gull!

There was good news and bad news when it raised its wings again, as the expected whole set of primaries, lacking any moult gaps, wasn't to be seen. Instead, it was missing P4 and growing P3, having already replaced P1-2. This superficially put it behind the local 2cys which were already replacing somewhere between P6-8, but whilst they were replacing juvenile primaries (faded, brown, and pointed) with 2nd-generation feathers (blacker and round-tipped), my bird's existing primaries were all black and rounded, and the new P1-2 were 3rd-generation, blackish feathers with narrow white tips! So it was almost a year ahead of similar-aged birds alongside it, with regards to primary moult, putting it way out of range of even the most extreme intermedius.

The spread wing also revealed a full set of new, white-tipped secondaries (whereas the locals possessed large moult gaps in the secondaries, almost without exception), and a complete moulted tail. The greater coverts of the numerous 2cy graellsii present tended either to show gaps like in the secondaries, or were formed of a solid dark blackish band of brand-new, replaced feathers. The more worn greater coverts of the Baltic Gull were replaced over the winter along with the primaries, and so had seen more action.
So if so much of the plumage is so far advanced, why isn't it a 3cy graellsii or intermedius? The dark iris and dull bare parts suggest a 2cy, and the fact that the 2nd-generation primaries don't look too worn helps rule out the possibility too (the feathers would be a year old in a 3cy, rather than perhaps four to six months old in a 2cy fuscus).

It had been a year and a week since I was lucky enough to find a 2cy Baltic Gull in Lincolnshire, and some of the similarities were striking, as can be seen in the above pic, the Lincs bird on the left (also note the difference in appearance of the exposed primaries between the two birds of the same age in the righthand image). The Lincs bird was slightly behind this one in primary moult, but had dropped P1-2 by 23rd July.

Very similar bird by Hannu Koskinen in Finland in early July 2007

Whilst this bird could be considered almost too advanced, even for fuscus, at least three out of a sample of 50 birds examined by Visa Rauste in Finland had replaced P1-2 by the first week of August.
Oh, and as I tried to relocate it after a big flush of the flock, I came across the juv mich I'd been hoping for! (under the Baltic in the flight shot above).

The word from the experts was generally inconclusive, as the quality of the images (all taken on my iPhone) didn't allow the primaries to be aged with 100% confidence. But nobody said no...

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