Weather conditions and conspecific density influence survival of overwintering Dunlin Calidris alpina in North Wales

Abstract

Inter-annual survival rates of juvenile Dunlin Calidris alpina increased with wet weather conditions but decreased with the density of conspecifics in winter, ranging from 0.34 to 0.62 in the best model. Adult inter-annual survival remained high and constant at 0.72. Aims To estimate inter-annual survival rates of both adult and juvenile Dunlin in North Wales. To quantify the effects on survival rates of weather conditions and conspecific density. Methods Cormack-Jolly-Seber models in Program MARK were used to analyse 21 years of ringing data (1990-2011) from Traeth Lafan, NorthWales. Models were constructed using a two age-class structure. The influence of a range of weather conditions and WeBS census data on survival were examined. Results Adult survival was best modelled at a constant rate of 0.72 (se 0.008) across the 21 years. Juvenile survival rates were found to vary most strongly with total rainfall (mm) during the season and the number of conspecifics present. Survival rates varied from 0.34 (se 0.06) to 0.62 (se 0.09), with higher survival in years with high rainfall and low numbers of birds. Conclusion Survival rates of juvenile Dunlin are affected by both weather and density of conspecifics. These results have implications for the future of Dunlin in the UK when considering both climate change and habitat loss.