Decline Of Jackdaws Corvus Monedula In The City Of Zielona Góra

Abstract

Abstract The aim of the study was to determine the number and distribution of breeding Jackdaws Corvus monedula in different urban habitat types in Zielona Góra in 2012 and to compare the results with those from a 2004 survey. On the seven study areas, the highest density was recorded in Park Tysiąclecia with 6.0 pairs per 10 ha, followed by the plot Słoneczne with 3.5, the Old Town with 1.0 and the plot Winnica with 0.4. On the plots Zacisze, Chynów and Industrial Zone, foraging Jackdaws were noted but we did not find any indication for breeding. From 2004 to 2012, the number of Jackdaws declined on the plots Słoneczne and Old Town. On the plot Winnica the number of breeding pairs remained the same. In Park Tysiąclecia Jackdaws increased from two pairs in 2004 to six pairs in 2012. This increase may have been caused by the settlement of birds formerly breeding in the Old Town where numbers were declining, probably due to the loss of suitable nest sites. The most likely causes for the overall decrease of Jackdaw numbers in Zielona Góra include renovation, modernisation and thermal insulation of buildings in the Old Town and in housing estates, leading to a decline in space available for nesting. Other significant factors are the lack of food sources in the city centre and an increasing degree of urbanisation. Furthermore, the city is surrounded by dense pine monoculture which undoubtedly has a negative influence on the number of Jackdaws.