Bird ringing in Britain and Ireland in 2003

Abstract

This is the 67th annual report of the British Trust for Ornithology's Ringing Scheme, covering work carried out, and data received, in 2003. During the year, reports of ringed birds were used to assess the post‐release survival of rehabilitated individuals. Varying proportions of different species were able to re‐enter the population, with Mute Swan Cygnus olor being the most successful. The origins and age structure of Guillemots Uria aalge ringed in Britain & Ireland and found dead after five major oil spills in European waters were found to vary depending on the location of the oil spill. More immature birds and birds from eastern colonies tended to be found after spills that were further south, whereas spills in the north had a greater effect on adults and birds from western colonies. Work on mass gain strategies in Blackbirds Turdus merula showed that they put on mass in winter, when the threat of starvation is greatest, as well as changing mass through the day, again probably in response to the likelihood of starvation. A study of the survival of passerines in the few weeks after fledging found that the survival rate during this critical period is only aboutone sixth of the rate in the rest of the first year of life. A study of the demography of Spotted Flycatcher Muscicapa striata showed that changes in post fleding survival were the most likely mechanism for the observed population decline. Data gathered as part of the Constant Effort Sites (CES) Scheme showed that adult abundance among resident species was generally high, following a good breeding season in 2002. When compared to 2002, fledgling productivity in 2003 was lower, probably as a resultof cold, wetweather during the breeding season. A total of 111 Retrapping Adults for Survival (RAS) studies submitted data covering 43 species. Target species for future workwere identified. Continuing work on the winter movements of farmland passerines showed variations in the distances moved by different species. Over 11,000 Swallows Hirundo rustica were ringed aspartofthe Swallow Roost Project. The total number of birds ringed (848,532) increased for the second year and was 5% above the mean of the previous five years (1998–2002). The recovery total (11,554) was also 5% up on the five‐year mean (1998–2002). Recoveries of 180 BTO‐ringed birds and 76 ringed abroad are presented in the report; those included confirm known or suspected movement patterns or are unexpected movements.