Saturday, 19 December 2009

Wknd 19-20 December

It was bleak at Ferny Ness at noon on Saturday, and Great Blackbacks had appeared in greater numbers than usual, 11 on Gosford Sands, a 1st-win shown above, with Cockenzie power station behind and the snow-covered Pentlands beyond. The Stonechat was active as ever but again no Chiff. Nearby a male Blackcap was lurking in buckthorn along the Old Coast Road, new for NT47N.

There was an article published recently summarising the work done on German breeding Blackcaps which have been found to comprise 2 sympatric (geographically overlapping) breeding populations - the original group which migrate SW to Spain and a new bunch which go NW to the UK (BBC summary). The latter are found to have narrower bills, which has been explained as matching their feeding preference of "primarily seeds and fat at garden feeders". However, the latter is rather speculative, as it presumes we know how many are out there not visiting gardens, as per today's bird! The latest local map is certainly indicative of a strong urban correlation (turn on "Major towns", lower left) but given the garden feeding habitat and associated concentration of human observers (cf also the Chiffchaff map, a species which doesn't use feeders) it would seem unwise to draw any firm conclusion on the overall numerical dominance of feeder users. Also, the reference cited in support of British winterers relying on artificial feeding is actually a general study on garden feeding, where Blackcap showed one of the lowest rates of increase amongst the 21 species found to have increased (1970-2000); no reference is made to the proportion using gardens as opposed to more natural sites, though evidence for a trend towards earlier arrivals is also noted. Other aspects of this "incipient speciation" are discussed further on this blog and it is clear that more work will be needed to fully unravel these mysteries. Meantime, let's keep mapping them.

Children's parties again Sunday but called in at Eskside and photo'd some typical immature European Herring Gulls, as per below - 1x 1st-win, 2x 2nd-win, 1x 3rd-win, plus a 1st-win BHG. Also there, pr RBM some distance upstream. At Seton harbour gull numbers had increased again and a large blue-backed Herring Gull was present, i.e. a northern argentatus (right).

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