Bird ringing in Britain and Ireland in 1997

Abstract

This is the 61st annual report of the British Trust for Ornithology's Ringing Scheme, presenting research carried out and data received in 1997. Work examining the survival rates of 31 farmland passerines in relation to long‐term changes in abundance suggested that changes in survival rates for 16 species had, to some extent, influenced their abundance. This was particularly important for a number of declining species. Other research examined the post‐release survival of oiled, cleaned and rehabilitated Guillemots and demonstrated that these Guillemots had lower annual survival rates than non‐oiled, non‐rehabilitated birds. Important recommendations about the future monitoring of the effects of rehabilitating oiled seabirds were made as a result of this work. A review of avian survival rates was also carried out in 1997, which brought together reliable survival rates for 115 species. The successful launch of the Retrapping Adults for Survival (RAS) Project is reported, together with an outline of its methods. This project aims to gather important data on the survival of a wide range of species in the UK, using targeted trapping for specific species and mark‐recapture analyses. Data collected from the Constant Effort Sites (CES) Scheme indicated that the 1997 breeding season was better than that in 1996 for the majority of passerine species monitored. However, significantly fewer adult birds were caught at Constant Effort (CE) sites in 1997 than in 1996 for four resident insectivores (Wren, Robin, Blackbird and Song Thrush), one resident seed‐eater (Bullfinch) and three trans‐Saharan migrants (Sedge Warbler, Reed Warbler and Whitethroat). The declines in adult numbers for four of the ‘Red‐listed’ species (Song Thrush, Linnet, Bullfinch and Reed Bunting) continued. Long‐term declines in adult catches of Blackbird and Song Thrush on CE sites were found to be similar, possibly suggesting similar causal factors. The value of the CES Scheme was further demonstrated by a new analysis examining long‐term trends in abundance of species monitored on CE sites. Comparison of these trends with those from other monitoring schemes (eg Common Birds Census) highlighted the confidence that can be placed in such survey methods, together with the tremendous conservation value of these schemes. The number of birds ringed in 1997 (800,362) was 6% down on the total for 1996 and 5% down on the five‐year average for 1992–1996. The number of ‘Red‐listed’ Birds of Conservation Concern species ringed in 1997 was down by 7% on the five‐year mean, while the number of ‘Amber‐listed’ species was down by 8%. The recovery total (11,210) is the lowest since 1972, and possible reasons for this are discussed. Recoveries of 122 BTO‐ringed birds and 61 birds ringed abroad are presented in the report, including a number of significant movements of an unusual nature. Particularly noteworthy were: (i) the movement of a Cormorant from Essex to Tunisia, (ii) the movement of a Red Kite (descended from the re‐introduction programme) from Scotland to Iceland and (iii) the movement of a Wren from Russia to England.