Per capita production of young and adult female survival drive population dynamics of a duck flyway population

How and why animal populations change over time and across different regions are fundamental questions in ecology. Comprehensive insights into these questions can be achieved by jointly estimating demographic rates, demographic mechanisms of population change and environmental drivers of demography. We incorporated all available demographic data from the Northwest Europe wintering population of Eurasian wigeon ( Mareca penelope ) into an integrated population model to estimate population development and structure, demographic rates, contributions of different demographic rates to population change, and the environmental drivers of demography from 1976 to 2023. The population approximately doubled during this period, and temporal variation in population growth rate was driven mainly by changes in per capita production of young and female survival. Per capita production of young was positively affected by spring flooding and temperatures during brood rearing. Density dependence had a negative effect on per capita production of young. Cold winters reduced annual survival. Our findings emphasize the dominant role of per capita production of young in population dynamics for species like wigeon, highlighting the need for conservation plans that explicitly consider environmental drivers of reproduction. We also demonstrate that a warming climate can have multiple demographic effects across seasons.