Urban Cooper's hawks outcompete their rural neighbors

Date:December 13, 2017

Source:American Ornithological Society Publications Office

Summary:Depending on whether a species flourishes in a city environment, urban wildlife populations can be 'sources' or 'sinks,' either reproducing so quickly that individuals leave to colonize the surrounding area or needing constant immigration from outside to stay viable. A new study examines the population dynamics of Cooper's hawks in urban Albuquerque, N.M., and finds that city-born birds aren't just thriving -- they're actually forcing their rural neighbors out of their nest sites.

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Great tits' 'black ties' smaller in the city

12 June 2014 Last updated at 01:27

By Michelle WarwickerReporter, BBC Nature

Urban great tits have smaller black breast stripes than their rural neighbours, a study has found.

Scientists discovered significant differences between birds living in Barcelona, Spain and a nearby forest.

Smaller "black ties" appeared to improve male great tits' survival rates in the city, while in the countryside birds with larger ties fared best.

"The urban habitat favours a different kind of bird than the natural habitat," said researcher Dr Juan Carlos Senar.

His team captured and recaptured birds over several years and used a predictive computer model to compare survival rates of great tits with different sized ties.

"Recapturing a bird means that it is alive, and so we can relate survival probability to tie size," explained Dr Senar, who is head of research at the Natural History Museum of Barcelona.

The size of the distinctive black stripe on great tits' yellow chests is hereditary. It varies more in males, and is linked to their personality.

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