These research results are published by Claudia Wascher and Kurt Kotrschal from the Konrad Lorenz Research Center of the University of Vienna, as well as Walter Arnold from the University of Veterinary Medicine Vienna in "Scientific Reports". In winter, the animals "save" their energy reserves in order to "invest" them in reproduction.
Wascher, C.A.F., Kotrschal, K., Arnold, W. Free-living greylag geese adjust their heart rates and body core temperatures to season and reproductive context. Scientific Reports, volume 8, Article number: 2142 (2018) doi:10.1038/s41598-018-20655-z
