Bird-eating raptors reap rewards of city life

Bird-eating raptors are adapting just as well – and in some cases better – to life in towns and cities than their natural habitats, research by Nottingham Trent University suggests.

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Peregrine falcons are thriving in towns and cities

A plentiful supply of food means specialist bird predators such as peregrine falcons, Cooper’s hawks and northern goshawks are thriving in their new urban environments.

It’s not such good news for their mammal-eating counterparts, however, who typically struggle to adjust to their new urban homes where food is more scarce.

Bird-eating raptors are breeding more successfully, with bigger clutch sizes and more chicks fledging the nest, the researchers found.

The study – led by the university’s School of Animal, Rural and Environmental Sciences – involved comparing more than 30 studies of urban and rural populations of raptors across the world.

While mammal-eating birds, such as kestrels and owls, might flourish in rural environments, they fared less well in urban surroundings due to a lack of available prey and – in some cases – increased human activity, the study suggests.

The researchers, writing in the Journal of Ornithology, argue that some raptors may be falling into an ‘ecological trap’, whereby the habitat appears attractive but it is actually of poor quality.

Raptors in general bred earlier in urban environments – in some cases over a month earlier – the researchers found.

This could be due to the year-round availability of prey for bird-eaters and higher temperatures.

Artificial light may also be playing a part, making it easier to hunt at night, as well as giving a false impression of day length.

Peregrine falcons and Cooper’s hawks produced 1.1 and 1.2 more chicks respectively in urban environments. Mammal and insect-eating burrowing owls and Eurasian kestrels, meanwhile, produce 0.5 and 1 fewer chicks at urban sites.

While many raptors typically nest on cliff edges and open landscapes, in recent years they have started nesting on tall buildings in towns and cities, which mimic these conditions. Peregrine falcons have nested on a ledge of Nottingham Trent University’s Newton building in the city centre for many years.

“Raptors are increasingly associated with towns and cities – but urbanisation has mixed fortunes for birds of prey,” said Nottingham Trent University researcher Esther Kettel.

She said: “Our study suggests that availability and type of food is likely to be one of the most important determinants of success for urban-nesting raptors.

“Specifically, bird-eating raptors such as peregrines appear to adapt positively to urbanisation, whilst those that feed on small mammals, such as Eurasian kestrels, do less well.”

“Understanding breeding performance of these iconic birds in urban and non-urban environments is essential for aiding future conservation and management efforts.”

The research also involved University College Cork.

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Bird-eating raptors reap rewards of city life

Published on 14 September 2017
  • Subject area: Animal, equine and wildlife
  • Category: Press; School of Animal, Rural and Environmental Sciences

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