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Dispersal is a key process in population and evolutionary ecology. Individual decisions are affected by fitness consequences of dispersal, but these are difficult to measure in wild populations. A long-term dataset on a geographically closed bird population, the Mauritius kestrel, offers a rare opportunity to explore fitness consequences. Females dispersed further when the availability of local breeding sites was limited, whereas male dispersal correlated with phenotypic traits. Female but not male fitness was lower when they dispersed longer distances compared to settling close to home. These results suggest a cost of dispersal in females. We found evidence of both short- and long-term fitness consequences of natal dispersal in females, including reduced fecundity in early life and more rapid aging in later life. Taken together, our results indicate that dispersal in early life might shape life history strategies in wild populations., (© 2013 Blackwell Publishing Ltd/CNRS.)

Population dynamics can be regulated through intra- and interspecific density dependence. In species with close ecological requirements, interspecific competition for resources may add to intraspecific density, or even exceed its effect; it may impact single or multiple traits. However, the relative impact of intra- and interspecific densities on demographic parameters has been rarely empirically assessed. We analyzed 18 years of capture-mark-recapture data from brown trout (Salmo trutta) coexisting with Atlantic salmon (Salmo salar) during the juvenile freshwater phase in the Oir River (France) to estimate the relative effects of intra- and interspecific density on trout early life. In trout, a species with optional migration, we estimated the migration probability of young-of-the-year trout out of their natal site, survival probability during the first winter, as well as body size, in relation to both intra- and interspecific density. Trout density correlated negatively with body size and with winter survival in resident trout but not with trout migration. Salmon density correlated positively with trout migration, but no impact was detected on trout body size or survival. Our study highlighted contrasting effects of intra- and interspecific density on trout early life, and the need to account for both factors when studying population dynamics in coexisting species. In particular, by affecting trout migration decision, salmon density may drive trout life history. [ABSTRACT FROM AUTHOR]