Piotr Jadczyk
Ornis Polonica 2015, 56: 275–286
https://doi.org/10.12657/ornis.2015.4.1
Abstract: The paper describes abundance dynamics of Rooks Corvus frugilegus and Jackdaws C. monedula, during two winters at two rubbish dumps – in Gać and Opole (Silesia, S Poland). The dumps were surveyed once per week, with species counted separately; in case of Rook, age classes were also noted. Both species were regularly present at the dumps. Their numbers peaked in the middle of the winter and on average, Rooks were more abundant than Jackdaws. The numbers depended on winter season (2007/08 and 2008/09), site and were non-linearly related to the average air temperature (birds were more abundant during colder periods). No relationship between snow cover and abundance was found. The percentage of immature Rooks at Gać rubbish dump was 24% during 2007/2008 winter, 40% during 2008/2009 winter and 1.7% at Opole during 2008/2009 winter. High numbers recorded during the study indicate that both sites represent attractive feeding sites for both species, particularly during cold periods.
Keywords: abundance, Corvidae, Corvids, foraging, rubbish dumps, wintering
