Fruit removal from rowanberry (Sorbus aucuparia) trees at urban and rural areas in Finland: A multi-scale study

Abstract

Urbanization changes landscape, causes destruction of natural habitats, and reduces species diversity. Urbanization can alter the interaction between fruit-bearing plants and frugivorous birds such as the Fieldfare, Turdus pilaris, and Bohemian waxwing, Bombycilla garrulus, which are the most abundant frugivorous bird species in Finland. Rowanberry, Sorbus aucuparia, is an ornamental tree species used commonly in the urban landscaping. It can promote bird diversity and the pleasantness of the urban environment for humans. The study was conducted on three spatial scales ranging from the macro scale (600km latitudinal gradient) to the regional scale (rural vs. urban habitats), and to the micro scale (different tree parts) in three towns and their nearby rural areas in Finland. About 25 trees were photographed on each site three times during the autumn until the rowanberry fruit-crop had been used up. At the beginning of the research the crop size was larger on the urban trees than that of rural ones. The fruit removal rate was not related to the geographical location. However, in urban habitats the fruits were consumed later than in rural habitats. At the tree-level, the rowanberry fruits were removed earlier at the tops of trees. Our results suggest that earlier use of rowanberry fruits from rural habitats and tree tops may be related on human and predator-related disturbances. Our results indicated that urban rowanberry fruit crop is important food resource for frugivorous bird species in urban areas.