Monday, 14 March 2011

Granby, Sunday 13 March

The weather forecast had been pretty awful, but thankfully it was wrong and it turned out to be a perfect ringing day. The birds trickled in steadily and we finished on exactly 100 birds. We could have caught more had we not had to leave due to other engagements which was a pity as the last couple of rounds started to produce the older retraps.

Yellowhammers made up a third of the catch and Great Tits almost a quarter. 6 Reed Buntings was the best ever day total for the site and Great Tits continue to outnumber Blue Tits. We caught a second Great Tit retrap from nestbox 8 in as many visits but star bird was an old Chaffinch, ringed as 3M on 14/11/2004 and not caught since.

Break down of the catch (new/retrap) as follows: Yellowhammer (26/7), Great Tit (6/17), Blue Tit (5/10), Chaffinch (8/1), Reed Bunting (5/1), Tree Sparrow (5/0), Blackbird (3/0), Dunnock (1/0), Wren (2/0), Robin (1/0).

We spent quite a bit of time looking at alulas today. Firstly on Yellowhammers it would seem to be useful when aging birds as youngsters often have a visible moult limit, but usually only at the smallest of the the three feathers. Most young birds seem to replace this feather, but not the larger two (so the alula score is still zero). But as can be seen below (I hope), the fringe of this smallest feather is golden yellow, matching the replaced lesser coverts and contrasting with the buffy fringe of the middle feather. Furthermore the central part of the feather is dark grey as opposed to the browner juvenile feathers. We did catch a single youngster that had not moulted this feather today, and it had a clear ginger-brown fringe.

Then for some time we've been scratching our heads when trying to determine alula scores for Great Tits. The middle feather (which scores 1) is nearly always straight-forward with retained juvenile feather being slightly greenish-blue. However, the larger feather is very similar when replaced. Today we caught a young Great Tit that appeared to have replaced the large feather on one wing but not the other. The differences were slight, but noticeable:

Away from the nets, spring was attempting to make itself known with several bumble bees, some tiny bunnies, displaying Lapwings, and singing Skylarks. Other birds of note were several Buzzards, Golden Plovers and a lone Cormorant overhead.

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