Changes In Tree Sparrow Passer Montanus Populations From Urban Parks

Abstract Studies of local Tree Sparrow Passer montanus populations from urban parks of Polish cities reveal changes in abundance and in nest site selection which differ from data collected from farmland. These changes are not always synchronous among neighbouring cities and parks. Several urban declines are difficult to explain, chiefly when obscured by the changes in the number of artificial nesting sites. One such case was a recorded decline Tree Sparrow and a switch to nesting in buildings observed in the Szczytnicki Park of Wrocław, after colonization by pine martens Martes martes. Judging from this the absence/presence of important predators or nest predators in other urban parks of Polish cities may be an additional factor promoting Tree Sparrow declines. It is suggested that a lack of precise data on the intensity of (mosaic-like in time and space) predation pressure in agricultural and urban landscapes should be considered when explaining the reasons for population changes in other bird species.