Song Post Height in Relation to Predator Diversity and Urbanization


Anders P. Møller, Laboratoire d’Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, Bâtiment 362, F-91405 Orsay Cedex, France.


Birds may sing from positions in the vegetation (song posts) to allow efficient transmission of sexual and territorial vocal displays while simultaneously minimizing the risk of predation because of avian and mammalian predators. Because urban areas are deficient in specialized avian predators, but have many cats while the opposite is the case for nearby rural areas, urban birds should display higher in the vegetation. In a comparison of the abundance of predators in three cities (Oslo, Brønderslev, Orsay), I show that avian predators are more common in rural areas, while mammalian predators are more common in urban areas. Singing birds sang from higher positions in the vegetation of urban than nearby rural areas. Differences in song post heights between urban and rural areas were consistent among cities, suggesting inherent specific difference in microhabitat choice. Bird species that have become urbanized recently had similar song post heights in urban and rural habitats, while species that have been urbanized for a long time sang from relatively higher song posts in urban areas. These findings suggest that urban and rural birds differ in habitat use when singing. These differences in song post choice between urban and rural habitats may have a number of consequences for vocal displays in the two different habitats.