Community Structure and Nest Predation in Urban Parks and Rural Forest Patches

Urbanization can have a negative influence on the local biodiversity and biological communities. Especially ground-nesting birds are dependent on vegetation structure, green area size and ecological corridors. Urbanization is also proposed to alter the predator-prey interactions in city areas. We tested the effects of urbanization on ground nests using artificial nests and plasticine eggs. We compared nest predation rates and predator groups between 30 urban parks in the city of Turku and 30 forest patches in the rural countryside outside the city. The predator groups were assigned to be either corvid or mammal based on the bill or teeth marks on the plasticine eggs. We also tested the effects of the proportion of tree cover to nest predation rates in all study areas. In addition, we used standard bird counting methods to assess species abundances within a 50-meter radius from every nest site. Nest predation rates in urban parks were the same as in rural forest patches. Furthermore, there was no significant difference between predator groups comparing urban and rural areas based on the predation marks left on the plasticine eggs. However, there was an interaction in nest predation rates between the type of study site and the area of patch. In urban parks, nest predation rates were lower in larger than in smaller patches. In the rural sites, the trend was opposite. The total species richness and abundance did not differ between urban and rural areas, but the abundance of ground nesters was higher in rural areas compared to urban areas. The method of using artificial ground nests and plasticine eggs proved to be successful and could also be used to study predation on shrub nests