Friday, January 05, 2007

Winners and Losers (thus far)

Preliminary results have been released from the CES ringing project. CES stands for Constant Effort Site and consists of ringers setting the same number of nets, in the same place, for the same period of time for 12 ‘sessions’, at predetermined intervals, throughout April to September. From this ‘enforced’ standardised ringing the resultant number of birds caught each year can be used to monitor changes on previous years. Nationally CES has the ability to monitor changes in population size, breeding success and, for more common species, adult survival rates.

The early results from data submitted for 2006 appear to indicate that Robin (14%) Blackcap (10%) Blue Tit (22%) and Bullfinch (14%) are all statistically significantly down on adult numbers compared to last year, while Whitethroat (58%) and Greenfinch (27%) are up.

For breeding productivity Wren, Dunnock, Cetti’s Warbler (61%) and Chiffchaff are all down, with Blackbird, Sedge Warbler, Reed Warbler, Blue (69%) and Great Tit significantly increasing. Long term productivity trends are slightly different - Cetti’s Warbler (55%) and Chaffinch (39%) show significant increases but, more worrying Linnet (56%), Willow Tit (49%) and Willow Warbler (12%) declining. Lesser Whitethroat (21%) and Goldfinch (28%) are also declining but these values do not reach statistical significance for these species.

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