A review of CES captures 1981-2020

 Total captures: 

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CES involves 12 visits, but not all were completed in some years. In 1981 visits 7-12 were missed and visits 9-12in 1982-84. These later visits were compromised by our more frequent ringing sessions to monitor warbler migration. Since these early years only a few visits have been missed - in 1988 (visit 6) and in 2020 (visits 1-3). The running annual average total number of captures was about 380 birds Up to 2009. From 2010 onwards there was a step up to an average of about 420 birds per annum. We were able to fence an additional area (between gn3 and gn4/5) to exclude stock in 2004, and the breeding birds have probably benefited from the improved habitat. The peak total captures reflect years with better breeding success, 2010 being an especially productive year.

NFY captures: 

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Years with the best productivity (e.g., 1993, 1998 & 2010) and those with the worst productivity (e.g., 2001 & 2016) can be easily picked out, by relating the numbers of first years compared to the number of adults caught, but note that incomplete coverage in some years will give apparently better/poorer productivity. The missed visit periods would have particularly affected 1st year capture totals in 1981-84 & in 1988 and would have mainly affected adult captures in 2020. The step up in mean total captures (as noted above) appears to be due to higher numbers of NFY 1st year birds being caught, with NFY adults showing more stability across the review period.