Zebra finch on a rollercoaster: impact of temperature fluctuations on physiology, learning and memory

Climate variability and unpredictability present animals with challenging physiological and behavioural demands. However, empirical studies on endotherms involving manipulated environmental variability remain limited. This study investigated how temperature variability during development and adulthood, and the effect of mismatch between these stages, impact physiological responses and learning performance. Zebra finches (Taeniopygia castanotis) experienced either stable or variable ambient temperature conditions during early development and as juveniles. We assessed the colour-associative learning performance of juveniles (52-62 days old) and measured their accumulated feather corticosterone (fCORT) levels at approximately 80-95 days of age. Birds exposed to variable temperatures during development had higher fCORT levels and longer latency to choice in the learning test than those in stable conditions. However, we found no effect of temperature treatment or fCORT level on associative learning performance, as birds performed equally well under all temperature conditions. Furthermore, higher fCORT levels were associated with lower participation rates. We then randomly assigned half of each family's offspring to the opposite conditions after independence (95 days old) and evaluated whether developmental fCORT levels affected memory retention and adult learning. The behaviour of adult birds differed from that of juveniles and was affected by the mismatched temperature environment. The birds that moved from stable to variable conditions had shorter latency to choice. Contrary to our prediction, memory retention was uniformly high across treatment groups. Temperature variability did not affect associative learning accuracy or long-term memory, but variability was associated with differences in participation and with elevated fCORT.