Wintering and Stop-Over Areas of Grey Herons (Ardea cinerea) Breeding in Central Europe: A Ring-Recovery Analysis

We analysed migration distances of sub-adult and adult grey herons (Ardea cinerea) ringed in Poland between 1932 and 2014 when migrating to wintering and stop-over areas. The research was based on 239 ring recoveries during non-breeding periods from 92 ringing sites in Poland. We used location of ringing sites, age of bird, and year of recapture to explain variation in the observed distances between breeding and stop-over as well as wintering areas. We found variation in the location of non-breeding areas of grey herons from northern and southern Poland. Migration distance of grey herons increased with latitude, with birds from northern Poland spending the non-breeding period further away than birds from southern Poland. Considering possible shortening of the migration distance due to climate change, we analysed frequency of recoveries from the vicinity of the breeding site, Mediterranean and sub-Saharan zones. Despite reported claims of climate change leading to migration distance becoming shorter, we found that distance to those areas was not affected significantly by year. In contrast to previous studies made in western Europe, age of bird did not affect migration distance.