Original Paper

Behavioral Ecology and Sociobiology

, Volume 64, Issue 3, pp 409-418

Open Access This content is freely available online to anyone, anywhere at any time.

Habitat-related birdsong divergence: a multi-level study on the influence of territory density and ambient noise in European blackbirds

  • Erwin A. P. RipmeesterAffiliated withSylvius Laboratory, Behavioural Biology, IBL, Leiden University Email author 
  • , Jet S. KokAffiliated withSylvius Laboratory, Behavioural Biology, IBL, Leiden University
  • , Jacco C. van RijsselAffiliated withSylvius Laboratory, Behavioural Biology, IBL, Leiden University
  • , Hans SlabbekoornAffiliated withSylvius Laboratory, Behavioural Biology, IBL, Leiden University

Abstract

Song plays an important role in avian communication and acoustic variation is important at both the individual and population level. Habitat-related variation between populations in particular can reflect adaptations to the environment accumulated over generations, but this may not always be the case. In this study, we test whether variation between individuals matches local conditions with respect to noise level and territory density to examine whether short-term flexibility could contribute to song divergence at the population level. We conducted a case study on an urban and forest population of the European blackbird and show divergence at the population level (i.e. across habitats) in blackbird song, anthropogenic noise level and territory density. Unlike in several other species, we found a lack of any correlation at the individual level (i.e. across individuals) between song features and ambient noise. This suggests species-specific causal explanations for noise-dependent song differentiation which are likely associated with variation in song-copying behaviour or feedback constraints related to variable singing styles. On the other hand, we found that at the level of individual territories, temporal features, but not spectral ones, are correlated to territory density and seasonality. This suggests that short-term individual variation can indeed contribute to habitat-dependent divergence at the population level. As this may undermine the potential role for song as a population marker, we conclude that more investigations on individual song flexibility are required for a better understanding of the impact of population-level song divergence on hybridisation and speciation.

Keywords

Habitat-related song divergence Acoustic variation Anthropogenic noise Urbanisation Territory density Season