Long-term data in particular are valuable sources of information for clarifying the relationships between climatic and biological changes. For 29 years, the researchers collected detailed information on the start of breeding (i.e. date of the first goose egg laid in the flock) and breeding success (i.e. number of fledged young) of a total of 300 greylag geese in Grünau. The animals were settled in Grünau im Almtal in 1973 by Nobel Prize winner Konrad Lorenz; there are currently 157 birds in the flock. "Due to their persistence, the Grünau greylag geese are a unique and valuable resource for science worldwide," says ornithologist Josef Hemetsberger, who has been monitoring breeding events for 30 years. "Phenology deals with the developmental phenomena in nature that recur periodically throughout the year and is an important aspect of global change because timing patterns such as egg laying are strongly influenced by human activities. However, detailed analyses like ours are only possible using long-term data," explain co-authors Petra Sumasgutner and Didone Frigerio.
The study's findings in concrete terms: Since 1990, there has been a steady rise in temperature in the study area, with average annual temperatures increasing by 2°C. The generally warmer winters are causing geese to lay eggs earlier. This earlier onset of laying has led to an expansion of the overall laying window: "Warmer winters have allowed more females to begin breeding. Overall, more young have fledged," Didone Frigerio said. In general, then, greylag geese appear to be responding positively to warming, at least in the alpine region. "These results expand our understanding of the effects of environmental change at the population level. They open up new research approaches on the ecological consequences of climate change," concludes Sonia Kleindorfer, head of the research unit in Grünau.
Publication in Scientific Reports (2021):
Frigerio, D., Sumasgutner, P., Kotrschal, K., Kleindorfer, S., Hemetsberger, J..
From individual to population level: temperature and snow cover modulate fledging success through breeding phenology in Greylag geese (Anser anser); DOI: 10.1038/s41598-021-95011-9
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