Sunday, 1 December 2013

Oxwich Marsh 30 November

Very light northerly winds, meaning the nets were still, and food at the winter feeding station disappearing at a rate of knots suggested we were on for a big catch this week.  We were not disappointed, in numbers at least.  In total, 77 birds were processed.  The catch was as follows: blackbird (2), blue tit (48), great tit (5), dunnock (6), chaffinch (8), robin (3), reed bunting (4), great spotted woodpecker (1).

Unfortunately, despite the presence of flocks of finches that included siskin and redpoll, the catch was limited to common, mainly resident species.  However, these pose their own difficulties.  Photographs of a female chaffinch and a blue tit are below.

 
Female chaffinches pose particular difficulties in terms of ageing.  Sometimes retained greater coverts are clear in first winter female birds, but often the colour change between retained and new feathers is marginal or 'imaginable' as opposed to clear cut.  In some first winter birds the tails are narrow, pointed and battered, and a few have obvious growth bars.  The odd adult shows pristine, broad feathers.  However, in reality, many birds are inbetweeners.  Some young birds replace all or part of their tail during post juvenile moult, and they need a lot of grilling.  If in doubt, age code 2 (age unknown) is at least correct!
 
Blue tits, by way of contrast, are easy to age.  The difficulty here is getting them out of the nets.  While finches, buntings and warblers are often relatively easy to extract, blue tits are amongst the most difficult.  This is due to their agressive nature: they fight the net, and as a result get very tangled.  They also fight the extractor - grabbing net, twisting and biting, and tend to turn up in flocks.  In the hand, first winter blue tits typically retain one or more greater coverts, alula feathers, or (as a minimum) primary coverts. 
 
Hopefully next week will bring a more diverse range of finches - maybe even a brambling.
 
Many thanks to Heather Coats, Charlie Sargent, Aaron Davies and Laura Roberts for coming along for what was a hectic but enjoyable morning.
 
Owain Gabb
01/12/13


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