Abundance variations, survival and site fidelity of Reed Buntings Emberiza schoeniclus wintering in central Spain

Abstract

Populations of the Reed Bunting (Emberiza schoeniclus) have suffered serious declines in western Europe during the last three decades. However, information on population pa- rameters of migratory populations in their wintering quarters are scarce. Here, we exam- ine variations in abundance, apparent survival and philopatry of Reed Buntings wintering in central Spain during five winters (spanning a period of seven years) using capture-re- capture at a communal roost. Abundances were low during the first winters in the early 80s and increased steadily until the last winter in 1988-89. Model-averaged estimates, which account for model uncertainty, suggested that apparent survival fluctuations were small and did not follow any clear trend. There was some support for intersexual differ- ences in apparent survival, although model-averaged estimates were similar for both sexes, and low support for an effect of winter weather conditions on survival rates. Return rate was 81% after correcting for mean apparent survival (62%) and low recapture prob- ability (7%). However, this underestimates the return to the general area (feeding and roosting sites), because of high within- and between-roosts mobility of Reed Buntings during winter. Although population trends were not similar in different western European countries, our results are consistent with the overall recovery or stabilization of popula- tions after the severe declines during the 1970s. Moreover, minor changes in survival rates and probable stability of winter food supply point to higher productivity on breeding grounds as the cause of the observed increase in abundance.