Population dynamics of Black Redstart Phoenicurus ochruros on the Swedish West Coast during the 50-year period 1975–2024

Abstract

This paper aims to reflect the population dynamics of Black Redstart Phoenicurus ochruros during the 50-year period 1975–2024 in western Sweden. The results show a strong decrease in population size, averaging 70 %. Weedy areas with broken buildings, important for foraging and nesting, were widespread within the study areas during the 1980s. Extensive construction development has subsequently taken place in these areas. Changes in the breeding environments are likely the main reason behind the population decrease. In the study areas of Gothenburg, Varberg and Falkenberg, the habitat loss of breeding territories amounts to 92%. Additionally, there are likely several unknown factors contributing to the decrease in Black Redstart numbers in western Sweden, for example large-scale faunal shifts and climate change. The importance of source areas for the addition of individuals to marginal populations is well-known and could affect both immigration and expansion, as well as the decrease and disappearance of a species. Interspecific competition with Common Redstarts Phoenicurus phoenicurus is another factor that may be important. If the population trend reported here continues, there is an obvious risk that the Black Redstart will disappear as a western Swedish breeding species in the not-too-distant future.