Habitat selectivity during the annual life cycle of the grey Heron Ardea cinerea revealed by GPS-tracking

Abstract Background Patterns of habitats used by birds change throughout the annual cycle. GPS-tracking of birds enables, i.e. pinpointing foraging areas and preferred habitat types. There is a lack of detailed information on the habitat selection of the central European population of Grey Heron ( Ardea cinerea ) throughout the year. This study investigated the home range areas, foraging trips and habitat selectivity during the annual cycle in three GPS-tracked adult Grey Herons breeding in northern Poland and eastern Germany in 2012–2020. Results Home ranges of wintering and breeding grounds were similar, as well as ones of spring and autumn migration stop-overs. Foraging flights covered in winter (mean ± SD: 2.8 ± 11.5 km) were significantly longer than ones performed during breeding (0.8 ± 4.6 km). However, range of trips performed during incubation (0.4 ± 0.4 km) and chick-rearing periods (0.3 ± 0.6 km) were similar. Generally, individuals did not demonstrate a clear preference for any of the habitats throughout the year. Still, areas of aquatic habitats were significantly higher during autumn and spring migration stop-overs compared to wintering grounds. Periodically, individuals showed a preference for urban areas and pastures, while avoiding forests and non-irrigated arable land. All of those confirm the opportunistic/generalist character of Grey Heron’s habitat selectivity. Conclusions The patterns of habitat use in the studied Grey Herons were highly variable both on individual and intra-annual levels, indicating an opportunistic use of habitats. This is the first report on the habitat selectivity for the GPS-tracked Grey Herons from Central Europe.