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The article reports on the 2009 bird Ringing Scheme of the British Trust for Ornithology (BTO) covering Great Britain and Ireland to better understand population change. Due to low productivity in 2007 and 2008 and freezing winters, there were decreases in species such as Wren Troglodytes troglodytes, Sedge Warbler Acrocephalus schoenobaenus and Reed Warbler A. scirpaceus. The number of birds ringed was the highest recorded at 935,867 and recovery total was also high at 14,643.

Mark-recapture data from 20 years of standardized mist-netting were used to investigate site tenacity and adult survival rates of Wrens Troglodytes troglodytes and Treecreepers Certhia familiaris in an English woodland. Within breeding seasons, a high proportion of Wren (but not Treecreeper) recaptures occurred in the same part of the wood as the original capture. Between breeding seasons, a high proportion of recaptures of adult males (but not of adult females) occurred in the same part of the wood as the original capture. Both species experienced exceptionally high mortality during the severe winters of 1978-1979 and 1985-1986, and, in the case of Wren, all or almost all birds which had previously bred in the wood probably died. Outside of these two cold winters, apparent (minimum) adult survival rates of Wrens and Treecreepers showed very different temporal patterns of variation. Wren survival rates were negatively correlated with the number of snow days in winter, whilst Treecreeper survival was negatively correlated with the amount of winter rainfall. After allowing for the influence of winter weather, apparent survival rates of adult Wrens were density dependent, indicating that either mortality or permanent emigration out of the wood was density dependent. There was some evidence from British and Irish ringing recoveries that movements of adult Wrens may be density dependent. The apparent survival rate of adult Wrens was probably an important factor determining the size of the local breeding population. [ABSTRACT FROM AUTHOR]