Habitat preferences and territory size of the Dunnock Prunella modularis in southern Finland

Abstract

An area of 4.08 km2 was studied in Heinola, southern Finland, mainly in 1984-85. The mean song polygon size was 1 .53 ha (SD 0.42 ha, n=51) and, on average, unpaired males defended 0.27 ha smaller territories than paired males. The territories defended by two males were largest, averaging 2.17 ha (SD 0.54 ha, n=3) . Spruce-dominated forests were used disproportionatelly oftenbythe Dunnock. Statistically significant differences between the territories and control quadrats were found in 9 outof 18 habitat-structure variables. The most striking difference was the greatnumber of small spruces and spruce bushes in the territories . In addition medium-sized spruces were more numerous, the dominant trees were taller, and the canopy cover denser in the territories . In 49 outof 59 territories an edge of some kind was presentinside the territory or formed a boundary for the territory. In the upper tree layer of the territories, spruce was very prominent, but in the lower tree layer deciduous trees (mainly birch) were almost as numerous. In the bush layer deciduous bushes were most abundant . It is concluded that small spruces and spruce or juniper bushes are essential features of the habitat for the Dunnock; spruce bushes are important nest sites, and Dunnocks also search for food in thickcover under the deciduous and coniferous bushes . The males arriving earlypreferred young open bushy forests . In biandrous territories, the edge was nearer the centre and bushes were more numerous than in territories defended by one male.