CES 2018

Tony has now submitted our CES results to the BTO. We completed all 12 sessions again, with visit catches ranging from 15 (visit 4) to 76 (visit 7), and the total number of captures was 370. A total of 109 different adult birds were caught, which was the lowest since 2013, and below the average for recent years (123). The number of different juvenile caught was 202 (making productivity 1.85). Overall it was a below average breeding season (mean for the last ten years 1.95), though some species fared much better than others. Of our regularly caught species, Wren, Dunnock, Long-tailed Tit and Bullfinch saw more adults than young birds caught. In contrast, Robin, Blackbird, Song Thrush, Blackcap, Chiffchaff, Willow Warbler and Blue Tit saw over three times as many young birds as adults.

Since last year, the BTO have "crunched our numbers", and produced bar charts of annual capture rates across years, and species capture rates for 2017. We have added their summary onto our 2017 summary post, Please Click Here.

Over the years Jerry had been collating all our CES statistics into a spreadsheet which Peter has worked out some stats on:

• This years CES was, as mentioned above, a below average year with apparent low adult survival after the tough winter leading to low numbers caught early on in the season. 
• Although a decent productivity meant that things improved slightly as the season went on, only 3 (visits 1, 7 and 12) of the 12 visits were above the average of the last 10 years. Only those three and one other visit (11) were above the all time average, again indicating that it was, on the whole, a poor year. 
• However things are not bleak at the lake, as despite this the average of total CES captures over the last 10 years is nearly 13% higher than the all time average of total CES captures. NB: 2009-2018 average is: 434.50. 1985-2018 average is: 384.82
• This increase in total CES catches appears to coincide with the continued maturation of an additional area (immediately adjacent to the main part of our CES catching area). The group was able to fence this area in 2004, to exclude livestock. The habitat improved (as it matured), to become more suitable for feeding/nesting, and, we think, started to effect the catch from around 2006.
• The rise in the 10 year average (of total CES catches) has continued to rise in recent years, which re-enforces the belief that the habitat has improved (and continues to do so) - 2009-2018 average is: 434.50. 2006-2018 average is: 416.69. 1985-2018 average is: 384.82. The rise, in average CES total catch, since 2006 is 8%, but the rise in the last 10 years is nearly 13%.

Further analysis of the above, including any changes in productivity and adult survival and potential reasons behind this will hopefully be posted in due course.