Climatic forcing and individual heterogeneity in a resident mountain bird: legacy data reveal effects on reproductive strategies

Optimization of clutch size and timing of reproduction have substantial effects on lifetime reproductive success in vertebrates, and both individual quality and environmental variation may impact life history strategies. We tested hypotheses related to maternal investment and timing of reproduction, using 17 years (1978-1994) of individual-based life history data on willow ptarmigan (Lagopus l. lagopus, n=290 breeding females with n=319 breeding attempts) in central Norway. We analysed whether climatic variation and individual state variables (age and body mass) affected number of offspring and timing of reproduction, and individual repeatability in strategies. The results suggest that willow ptarmigan share a common optimal clutch size that is largely independent of measured individual states. While we found no clear direct weather effects on clutch size, higher spring temperatures advanced onset of breeding, and early breeding was followed by an increased number of offspring. Warmer s..., The ecological data was collected in 1978-1994 in Dovre, Norway.,