Bird ringing in Britain and Ireland in 1999

• Published in: Ringing & migration 2001-05, Vol.20 (3), p.239-288
• Main Authors: Clark, Jacquie A., Wernham, Chris V., Balmer, Dawn E., Adams, Sue Y., Griffin, Bridget M., Blackburn, Jeremy R., Anning, Dave, Milne, Linda J.
• Format: Article
• Language: English
• Subjects: Aves; Brackish; Freshwater; Marine
• ISSN: 0307-8698; 2159-8355
• DOI: 10.1080/03078698.2001.9674252

This is the 63 rd annual report of the British Trust for Ornithology's Ringing Scheme presenting work carried out and data received in 1999. A study of long-term trends in songbird productivity using constant effort ringing showed that changes have been markedly synchronised through time for some groups of ecologically similar species (eg resident insectivores, Blackbird and Song Thrush, Blue Tit and Great Tit). Significant decreases were found in the productivity (juvenile: adult ratio) of 15 of the 26 species, and no significant increases. For 14 species, higher temperatures over the summer months resulted in lower productivity, and greater total summer rainfall was associated with higher productivity for 11 species. Significant differences between regions of Britain & Ireland were detected for 11 species, highlighting the importance of maintaining sufficient numbers of monitoring sites to carry out analyses at the regional level. Comparison with nest record data showed that, for three species, the falling productivity may be a result of a decline in the number of nesting attempts or the immediate post-fledging survival of young. Some changes in productivity were linked to changes in abundance; for others a density-dependent negative change in productivity may have taken place and, for at least two species, changes in survival rates may be driving the observed population decline. Survival rates of adults of two declining species, Blackbird and Song Thrush, were measured using Constant Effort Sites (CES) data from 1983 to 1998. The annual survival of Blackbirds declined significantly and a strong relationship between annual survival rates and winter temperatures was found. A study of the declines in populations of Oystercatchers and Knot on the Wash found that winter survival rates of adult Oystercatchers have remained approximately constant (98%) from 1990 to 1998, except during three years of unusually low survival when both cockle and mussel stocks were low. Adult winter survival rates of Knot were more variable (70-97%). Indices of mussel and cockle stock size were significant in determining the over-winter survival rate of Oystercatchers but did not influence those of Knot. An analysis of ring-recovery and nest record data for Spotted Flycatcher showed that increasing mortality in the first year of life is likely to be responsible for the recent acceleration in the decline of this species. Data collected by the CES Scheme suggested that weather condi