The Sevenoaks Constant Effort Site

This is the seventh year of constant effort ringing at Sevenoaks which takes place at a site set up in scrub to the south of the East Lake.  One visit is made in every ten-day period from May until the end of August.  As can be seen from the table below all the twelve periods were covered by a visit representing about 132 hours of field work although one visit had to be abandoned half way through the session due to adverse weather conditions affecting the catch. Additional visits were made during the period but these catches are not included in the CES analysis.

Figures in brackets are for 2005
* weather-affected catch

 The capture table below shows the number of adult and juvenile birds of each species captured in 2006 compared with the catch in 2005. Some species are caught in such small numbers that attempts to draw conclusions from year-on-year comparison would be statistically unsound. Nonetheless, the more commonly caught species do show some interesting trends.
The total number numbers of birds caught this year was down by 12.8% this year (possibly in part due to the curtailed visit number 7) compared to 2005 continuing the trend of reduced annual catches ever since the study started at Sevenoaks. The reductions were mostly of juvenile birds which were down by 18.9% compared to the previous year. Over-winter survival of adult birds was patchy with good numbers of tits, treecreepers and migrant warblers making it through the winter and returning or remaining to breed in spring.  Other resident species such as wren, dunnock, robin, blackbird, song thrush and bullfinch faired less well and recorded a significantly reduced over-winter survival.

Turning to productivity, the majority of species showed a reduced number of birds fledging with wren, dunnock, song thrush, chiffchaff, blackcap, great tit and bullfinch showing marked decreases. Blue tits bucked the trend with a 200% increase in juvenile productivity.
Green woodpeckers, normally a strong feature in our CES captures were absent but greater-spotted woodpeckers fared well over the winter and had a good breeding season.
 

CES Captures for 2006

This table gives species totals for all captures during CES sessions.