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The learning advantage in urban bird life

Bird urban communities are poorer than those found in natural habitats. It seems that not all bird species can adapt to city life, even though many cities offer parks and gardens where many potential species could dwell.

We are interested in the mechanisms used by birds to communicate in noisy situations, and in this research we explored the possibility that birds differ in their ability to adapt their song to noisy habitats, which could explain the relative success of birds at surviving in the city. We know from previous studies that birds shift their song pitch upwards when noise levels are high; this should make songs more audible over low-pitched urban noise.

We hypothesised that this song modification would be easier for birds that learn to sing than for those that do not. A great divide exists in the songbirds, between species which need to learn their song from conspecifics, and those that can produce perfect species-specific song without previous exposure. We thus compared oscines and suboscines, two large groups of songbirds which differ in this aspect of behaviour. Oscines produce complex songs which are learnt from adult conspecifics, and suboscines have simpler songs that are faithfully genetically transmitted.

After two field seasons of fieldwork in Brazil and Mexico, studying 28 populations of 21 different species, we found that the degree of song adaptation to noise was stronger in oscines than in suboscines, suggesting that song learning helps birds adapt their song to noisy conditions. This difference is important in terms of bird conservation, since it informs us that the capacity of bird populations to withstand human alterations differs with respect to a behavioural trait. It also underlines the role of behaviour in allowing adaptation to a changing world.

Additional material for this study includes sounds and pictures.

The results of this research will appear shortly in the Journal of Evolutionary Biology, within an article signed by Ríos-Chelén, A.A., Salaberria, C., Barbosa, I., Macías García, C. and Gil, D., entitled : "The learning advantage: bird species that learn their song show a tighter adjustment of song to noisy environments than those that do not learn". The pre-print PDF is available on the left-side pannel of this page.

This research has been funded by the BBVA Foundation.

Pictures

  • Rufous-collared sparrow (Zonotrichia capensis)
  • Measuring noise amplitude levels
  • Recording bird song in Brasilia
  • BBVA Foundation