Crossness Nature Reserve

Constant Effort Ringing 2006

This is the fourth year of the Constant Effort ringing programme at Crossness LNR and it has proved to be a very interesting one; not only in terms of the number of species using the reserve but also the changes in productivity of some of the more common species. All twelve visits were completed in 2006 comprising some 78.5 hours of field work, or 37,680 net-foot hours. The overall capture totals were up by 13% on those for 2005.

The weather during the CES period was generally good with only two sessions recording light rain. However, as would be expected from such an exposed site, breezy conditions were not uncommon, especially towards mid-morning and on a number of occasions this may have affected the catch to some degree. As in 2005, temperatures rose quickly on many days and ringing was often concluded early, to avoid the worst of the heat.

Adult abundance
The more common resident species appear to have fared well over the winter, with increased numbers of adult Wren, Dunnock, Robin, Blackbird, Great Tit and Greenfinch recorded. Notably, adult Blue Tits were down by 44% although the sample size is rather small and Crossness is not ideal habitat for this species. The small Reed Bunting population appears to be increasing in size with 6 adults recorded during the CES period. No House Sparrows were recorded this year.

Migrants returned from their winter quarters in good numbers with increases for Reed Warbler and Whitethroat, the two principle species using the site. Oddly the number of adult Blackcaps recorded was down by 24% after the increases recorded for the last three years. Lesser Whitethroat was again recorded during the breeding season and at least two pairs of Chiffchaff bred on the reserve.

Breeding productivity
In general there was an increase in juveniles of 12% over the previous year. However, a number of resident species had a poor breeding season with Wren, Dunnock, Blackbird and Song Thrush all showing a fall in the number of juveniles recorded. Robins however did well and 25 juveniles were recorded during the period.

Although the number of Great Tit using nest boxes on the reserve increased and their productivity appeared to be high the overall number of juveniles of this species fell by 20%. The number of Reed Buntings caught each year is small but it was disappointing that the percentage of juveniles was down despite an increase in adult captures.

All the summer visitors had a good breeding season with excellent numbers of Reed Warbler, Whitethroat and Blackcap recorded.

The preliminary CES trends for 2006 recently issues by the British Trust for Ornithology for over 100 sites nationwide show that the biggest losers were resident species. This may be linked to poor weather at the start of the breeding season, and significant decreases in productivity were recorded for Wren (-28%), Dunnock (-31%).  However, tits bounced back after a poor year in 2005, with productivity up 69% for Blue Tit and 34% for Great Tit. With the exception of Lesser Whitethroat, migrants did well with Sedge and Reed Warbler showing significant increases in juveniles.

CES Captures for 2006

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