Urban birds have evolved unique anti-predation behaviour

Avian species that are preyed upon in rural habitats possess certain behavioural instincts that increase the probability that they will survive an attack by a predator. Individuals of such species that have migrated to urban habitats have altered their anti-predation behaviour in order to counter the differing predator species. The process by which animals and plants modify behaviour from their rural-based ancestors in urban environments is known as urbanization.

The predator community in urban environments is mainly mammalian, with house cats being the major constituents, while carnivorous avian species are the predominant predator of birds inhabiting rural areas. Research groups based at the University of Granada and Paris-Sud University studied the escape behaviours of 15 species of bird, analysing 1132 birds in total. Their data showed that urban birds tended to wriggle less and showed more tonic immobility (an involuntary state of paralysis used to appear “uninteresting” to predators). Furthermore, urban birds were less aggressive and employed fear screams more frequently than their rural ancestors. The progression of such behavioural characteristics over time has been demonstrated through studies of areas that were urbanized at different points in time. Urbanized birds possess a competitive edge in avoiding predation by cats, whilst also stopping behaviours that are more beneficial in rural communities with higher levels of predation. The increased usage of alarm calls also enables birds to warn relatives living in close proximity of impending danger.

In general, city birds are less aggressive and instead use tonic immobility more frequently, while also employing alarm calls more often than members of the same species living in the countryside. Understanding the urbanization evolutionary process is important as it may help biologists prevent the extinction of avian species due to urban growth.