High density of breeding Common Sandpipers Actitis hypoleucos in the Middle Vistula River, Poland

摘要

The Common Sandpiper Actitis hypoleucos is a widespread, monogamous wader species, which nests mainly in riverine habitats (Cramp & Simmons 1983, van Gils et al. 2019). The population of Common Sandpipers in Poland is estimated to be 1,000-2,200 breeding pairs (Sikora et al. 2007,Chodkiewicz et al. 2015), and the breeding density varies widely, from 4 to 35 pairs/10 km of river (Dom-browski et al. 1994,Elas & Meissner 2014). There is a significant level of extra-pair paternity in this species, but there is no evidence of polygyny and few rare cases of polyandry (Mee 2001,Mee et al. 2004). During the breeding season, males defend multi-purpose territories for breeding, feeding and courtship that vary from 100 m to 500 m in length along a riverbank; nests are typically found no closer than 60 m apart (Yalden 1986,Mee 2001, van Gils et al. 2019).