Bird ringing in Britain and Ireland in 2002

Abstract

This is the 66th annual report of the British Trust for Ornithology's Ringing Scheme covering work carried out and data received in 2002. The BTO continues to work to understand the causes of bird population declines. During the year a major report on the demography of House Sparrows† and Starlings was completed. The work showed that while the decline in House Sparrows is likely to be due to a decline in the survival rate of first‐year birds, changes in productivity (the number of young birds entering the population) appear to have helped to halt the decline in recent years. For Starlings, changes in survival of first‐year birds was the best way of explaining the population decline, although changes in adult survival rate may also be implicated in eastern Britain. Work on wader age ratios showed that the proportion of juvenile waders in flocks caught in winter in Britain & Ireland may provide information about breeding success of high arctic species. Such data are hard to gather on the breeding grounds because of their remoteness and the dispersed nature of the breeding birds. A novel analysis of recoveries was able to show that the origins of Willow Warblers moving through Dungeness Bird Observatory in the autumn varied through the migration period and that the patterns of movement had changed in recent years. Data from the Constant Effort Sites (CES) Scheme showed that adult abundance in 2002 was generally lower than in 2001 following poor productivity in that year. Of nine significant changes in catches of adult birds between 2001 and 2002 eight were decreases (Blackbird, Sedge Warbler, Reed Warbler, Garden Warbler, Willow Warbler, Blue Tit, Great Tit and Chaffinch), with one increase (Bullfinch). Productivity generally improved when compared to 2001 with 18 species showing a statistically significant increase between the two years (Wren, Dunnock, Robin, Blackbird, Sedge Warbler, Reed Warbler, Whitethroat, Blackcap, Chiffchaff, Willow Warbler, Long‐tailed Tit, Blue Tit, Great Tit, Treecreeper, Chaffinch, Greenfinch, Bullfinch and Reed Bunting). Data sets for 110 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The number of birds ringed (791,074) increased, after the drop in 2001 as a result of some land access restrictions imposed due to Foot and Mouth Disease, and was 4% above the mean of the previous five years (1997–2001). The recovery total (11,042) was similar to the five‐year mean (1997–2001). Recoveries of 130 BTO‐ringed birds and 63 ringed abroad are presented in the report; those selected for inclusion confirm known breeding or wintering areas or migration routes and also show a number of significant or unusual movements.