Arkadiusz Sikora, Łukasz Ławicki, Przemysław Wylegała, Wiesław Lenkiewicz
Ornis Polonica 2015, 56: 1–24
https://doi.org/10.12657/ornis.2015.1.0
Abstract: To estimate numbers and distribution of Common Cranes Grus grus during autumn migration in Poland, counts of the species at 88–103 roosting sites were performed in 2009–2013. In 2009 two counts were carried out, and in subsequent years – three counts each season. A total maximum number of Cranes at all roosting sites was 93.000–120.000, and the numbers increased by about 7% a year. All roosting sites were located at lowlands, and the peak numbers were recorded in the northern and western Poland. In 2012–2013 46 and 53% of birds were found in the northen lake districts, 28 and 23% on lowlands in central Poland, and at the coast – 22 and 26%. At 6 sites flocks of more than 5.000 birds were recorded: the Warta Mouth National Park, the Lower Odra Valley, the Barycz Valley, Słowiński National Park, Nietlickie Marshland and the Middle Noteć Valley. Common Cranes roosted most often in river valleys – 47% individuals, at fish-ponds – 13%, lakes – 12%, peat bogs and calcareous marshes – 7% and flooded areas – 6%, while they used other habitats (fields, an open pit, sewage farms and sandbars in the river-mouth near a sea bay) much less frequently. In 2012–2013 in northern Poland (above 53°40′ N) maximum numbers were recorded only in September, while to the south of this line the largest flocks were generally observed in October. In 2009–2013 the share of young birds ranged 8–12%. The families had on average 1.30 young. In flocks consisting of up to 10 birds, the proportion of immature undividuals at foraging and roosting sites was 28%, and gradually declined with the increase of flock size, reaching 10% in groups of more than 100 birds. Among 123 sites visited in 2009–2013 and hosting at least 100 birds, as many as 74 (66%) are under some form of protection. About 20% of the global Crane population migrates across Poland, as well as about 25% of European population and about 30% of birds passing through central Europe using western and Baltic-Hungarian route.
Keywords: autumn monitoring, Common Crane, Grus grus, Poland, roosting site
