Half time update for CES

Andrew Harris & Roger Kiddie write:

After a trial year in 2012, we started two dry scrub Constant Effort Sites (CES) last year at the RSPB Northward Hill reserve. In 2012 we did the full 12 visits at one of the sites and seven visits at the other. The results from 2013 showed that adult survival was 37% down, but productivity was 23% up from 2012.

This year we speculated that with the mild winter, adult survival for resident birds would be up but we had no idea what the numbers of returning migrants, mostly Sylvia warblers, would be. We hoped that with a better breeding season than the last two years, productivity would also increase.



We have now completed the first six visits at each site. We have had 244 adults compared with 202 in 2013, showing a 20% increase. Residents have increased from 100 to 112 and migrants from 102 to 132. The species showing the largest increases are Dunnock (20 to 30), Blackcap (26 to 47), Wren (9 to 17), Lesser Whitethroat (10 to 19) and Chiffchaff (15 to 19). Whitethroat are the only species whose numbers have decreased (37 to 34).

Male Blackcap - Adrian Dancy

With the mild spring / early summer, juvenile numbers have been significantly up on last year (115 to 297) showing a near 160% increase. The most obvious increases have been in Blackcap (16 to 87), Wren (1 to 19), Robin (9 to 23), Dunnock (17 to 31), Blackbird (4 to 25), Blue Tit (25 to 48), Great Tit (6 to 19) and Long-tailed Tit (3 to 8). The only species obviously down at this stage of the season is Chiffchaff (19 to 16).

We are aware that our data aren’t representative of all the CES projects nationally, but we are encouraged by what appears to be happening on our site. We have 98 years’ worth of ringing experience between us but until 2012 we had never been involved in CES ringing. We have thoroughly enjoyed the experience and we feel it is good discipline both for us and our trainees and are happy to contribute to one of the BTO’s target ringing projects.