Signs of climate change impacts on the migration of Barn Swallow Hirundo rustica based on a 130-year time series

Long-distance migration is highly internally regulated; however, it has recently been shown that even for long-distance migrant species, the timing of migration, breeding and moulting can change under the influence of climate change. We studied the timing of spring and autumn migration of the Barn Swallow Hirundo rustica in Hungary in two periods (1894–1927 and 2005–2022) using 2,904 spring and 830 autumn migration records. In addition, we used 726 long-term recapture data from the Hungarian bird-ringing database to analyse changes in the birds' breeding and wintering grounds. Our results show that the spring return from wintering grounds shifted significantly earlier, while the start of autumn migration shifted significantly later. Based on sub-Saharan recapture data, we found that the species' wintering grounds shifted southward. In contrast, the breeding areas of the individuals ringed north of Hungary did not change significantly over time. Our findings suggest that climate change affects breeding populations of this species differently in different geographical regions. The earlier spring return affects the start of breeding, which, in the case of the Hungarian population, is a factor in the increase in the proportion of second and third broods.