Saturday, June 23, 2007

Cats could be scaring birds out of our cities

ARE cats frightening birds so much that they don't breed? Andy Beckerman and colleagues from the University of Sheffield, UK, think fear of cats may explain the ongoing fall in urban bird numbers.
Many accusatory fingers point to the cat, and in areas of high cat density, predation may indeed be the sole reason for the decline. It might not be cats' only effect, however. Beckerman's team built a model that took both kills and the fear factor into account, and found that apprehension could explain the decrease even where predation is low. A reduction of just one chick per breeding pair per year per cat can lead to a fall in bird numbers of up to 95 per cent (Animal Conservation, DOI: 10.1111/j.1469-1795.2007.00115.x).
"What's cool about the model is that with no mortality you still get a large decline through mechanisms of fear," says Beckerman.

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