How city birds’ bold, aggressive behaviour helps them rule the roost
Urban living isn’t for everyone, but certain birds can prosper in the environment
Most people probably wouldn’t consider bustling towns and cities good places for nature to thrive. Yet a few species of bird have so successfully adapted to city living that they boast large and thriving urban populations. Now, research has suggested that the success of these city-dwelling species may lie in their behaviour.
Urban habitats are quite different to the natural environments in which birds evolved. Cities are noisy places, they are lit almost continually with artificial lights and they contain an abundance of food. Cities are also full of people. This means birds living there rarely get any peace and must cope with almost constant disturbance from both humans and their pets.
But birds living in cities are known to be much more tolerant of human disturbance than their rural compatriots. In a study of 44 European bird species, all but four allowed humans to approach them more closely in cities than in rural habitats. This suggests that city birds are bolder in the face of a potential threat.
It’s not only towards humans that urban birds seem to be bolder. We recently studied the territorial behaviour of male great tits (Parus major) in cities and rural habitats in the UK, and found significant differences between them.
During the early spring, males of this species defend breeding territories. Once a male has a good territory he signals his ownership to other birds using song. In fact, together with attracting females, one of the main uses of song is territory defence.
When a rival male enters another’s territory and begins to sing, the territory holder usually responds aggressively to drive the intruder out. At first, this may mean simply singing back, but can quickly escalate to full-on physical conflict.
In our experiment, we used playbacks of great tit song to mimic an intruding male. This allowed us to measure how strongly urban and rural great tits respond to intruders. We found that city birds approached the intruder mimic 35 seconds faster and almost two metres closer than rural birds. This suggests that urban great tits are both bolder and more aggressive than rural great tits.
And it’s not just great tits which are known to be more aggressive in cities. Urban song sparrows (Melospiza melodia) have also been found to be more aggressive towards each other during the breeding season.
Why urban birds should be bolder and more aggressive than their rural cousins is not yet fully understood. One possibility is that in cities, where space is limited, only the most aggressive individuals are able to hold a territory.
Animal personalities
In addition to researching levels of aggression, we also looked at how consistent males were in their aggressive displays. This...
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