The Sevenoaks Constant Effort Site

This is the sixth 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. Additional visits were made during the period but these catches are not included in the CES analysis.

CES Visits During 2005

Figures in brackets are for 2004

 The capture table below shows the number of adult and juvenile birds of each species captured in 2005 compared with the catch in 2004. 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.

 A similar numbers of birds were caught this year as in 2004; the decrease in over-winter survival this year was compensated for by increased breeding productivity. Species which have done very well at Sevenoaks are Dunnock, Song Thrush, Bullfinch and Treecreeper. This success has been reflected in the draft national figures recently published by the BTO, except for the Song Thrush, which has continued to decline in other areas.  Robin, Blackbird and Wren all sustained higher than usual losses of adults over the winter but had a good breeding season which restored the population levels.  The picture regarding the tits is mixed with Long-tailed Tits doing badly, both over-wintering adults and breeding pairs. There is evidence that Marsh Tits bred on the reserve and although the numbers caught are small the presence of these birds is significant and welcome. Blue Tits and Great Tits appear to have suffered over the winter but for some unexplained reason while the Great Tits had quite a reasonable breeding season the Blue Tits did badly. Great Tits begin nesting and fledge earlier so they may have escaped the harsh weather in late spring  nationally both tit species had a disappointing breeding season.  

Turning to the migrant passerines, Blackcap arrived in good numbers but had a poor breeding season but for Chiffchaff the winter seems to have significantly reduced the number of adults which then suffered a further decrease with poor nesting success.  This picture accords with the national data.

From our capture figures Green Woodpeckers had a better year than Greater-spotted Woodpeckers although both species do well on the reserve.

CES Captures for 2005
This table gives species totals for all captures during CES sessions.