Heat stress inhibits cognitive performance in wild Western Australian magpies, Cracticus tibicen dorsalis

Cognition enables animals to respond and adapt to environmental changes and has been linked to fitness in multiple species. Identifying the potential impact of a warming climate on cognition is therefore crucial. We quantified individual performance in an ecologically relevant cognitive trait, associative learning, to investigate the relationship between heat stress and cognition in wild Western Australian magpies over 2 consecutive years. We found that heat stress had a significant negative effect on performance in both years, with individual pass rates much lower under heat stress than under nonheat stress conditions. The long-term repeatability of cognitive performance within temperature conditions was high (i.e. consistent fails under heat stress and consistent passes under nonheat stress conditions between years), but repeatability between conditions was low. This suggests that the observed effect could not be attributed solely to natural fluctuation in cognitive performance. This study is one of the first to reveal the negative influence of heat stress on cognitive performance in a wild animal, drawing attention to the potential cognitive consequences of rising temperatures.