Influence of the Mating System of the Eurasian Dipper on Sex-Specific Local Survival Rates

Abstract

The mating system of the Eurasian dipper (Cinclus cinclus) involves males defending resources, such as nesting sites or food, and females choosing sites based on quality. Strong territoriality and unequal quality of sites may induce polygyny. Depending on stream flow, external factors such as floods or drought may alter the quality of some breeding territories, leading to breeding dispersal. Emigration resulting from breeding dispersal should he reflected in annual local adult survival rates. In a study of the Eurasian dipper in northeastern France from 1981 to 1998, I verified that pairing and territoriality may influence local survival and that site choice may be mediated significantly by variation in extrinsic factors using mark-resighting data and selection of models using an information-theoretic framework. I found a decrease of about 0.09 in the annual adult local survival rates for both sexes of Eurasian dippers during flood years. During dry years and for monogamous dippers settled along <2m-wide brooks, female annual local survival rate decreased from 0.56 to 0.39, possibly reflecting permanent emigration, whereas the male resighting probability fell from 0.97 to 0.59, indicating delays in male breeding or temporary emigration. Unlike monogamous breeders, polygamous birds had constant local survival estimates and resighting probabilities, suggesting that they bred in sites secure from both flood and drought. Because the Eurasian dipper adapts poorly to environmental stress, 1 encourage managers to shorten stream diversions and other water management practices affecting stream flow.