Annual Bird Ringing Totals and Population Fluctuations

Abstract

Ringing of migrant birds has taken place at Ottenby, Oland, southeast Sweden since 1947. The effect of the winter weather in northwestern Europe on the wren Troglodytes troglodytes, of precipitation in the Sahel zone on the common whitethroat Sylvia communis and of the use of alkyl mercury compounds in Swedish agriculture on the yellowhammer Emberiza citrinella are clearly seen in the ringing figures. These examples illustrate the usefulness of ringing statistics for migrant birds in environmental monitoring.