A breeding bird survey was carried in the town of Assen, i.e. a section of the old inner city (37 ha) and in an industrial area (86 ha). In general, densities of breeding birds were higher in the old living-quarter (T able 2). In both areas, densities of forest species were strongly correlated to the number of trees (Fig. 3). However, densities were lower in the industrial area because trees were not mixed with bushes as in the old living quarter. In the industrial area, distributions of House Sparrow and Jackdaw were segregated, with House Sparrows breeding in houses and Jackdaws in factory buildings (Fig. 1). In the old living-quarter. Starlings preferred to settle in the vicinity of lawns and parks, which provided good foraging opportunities (Fig. 2). However, Starlings were absent from the proliferation of lawns in the industrial area, probably because these were too dry to use as foraging site. Presence of nest predators like the Magpie apparently had no impact on the local density of treeand bush-nesting passerines. In ha-squares with Magpie nests, the density of passerines amounted to 9.7 tenitories/ha; in squares without Magpies a lower density of 5.7 territories/ha was found.