Using different body size measures can lead to different conclusions about the effects of climate change

Aim: Declining animal body size has been proposed as a general response to increasing global temperatures that should be observed across a broad biogeographical scale. However, published studies have shown large variation in both the magnitude and direction of body size trends. We aim to investigate how the way body size is measured (body mass, structural size, body condition) may contribute to differences in body size trends between studies. Location: Semi-arid Australia. Taxon: White-plumed honeyeater (Ptilotula penicillatus). Methods: We studied two separate populations of P. penicillatus over 30 years to investigate the associations between weather and body size. We first investigated how body mass has been affected by weather conditions at each site and then determined how these same local weather conditions affected the constituent components of body mass (structural size and body condition). Results: The magnitude and direction of weather effects differed with...