City birds produce fewer, smaller chicks

MUNICH, Germany, Sept. 2 (UPI) -- A new study suggests life in the city diminishes the fertility of birds.

A team of researchers from the Ludwig Maximilian University and the Max Planck Institute of Ornithology found birds living in urban settings produce fewer and smaller offspring than birds in rural settings.

Scientists frequented 600 nest boxes of the great tit, Parus major, in the forest of Germany, as well as 156 nesting sites within the confines of Munich. Birds living in the Bavarian capital began laying eggs earlier than their rural peers. They also laid fewer eggs, and their birds left the nest weigh less than fledglings in born in the countryside.

During their nest visits, researchers measured temperature, humidity, light and noise levels, but their analysis revealed no correlation between these environmental factors and the discrepancies in clutch and fledgling size.

"Our study showed how difficult it is to accurately measure the effects of urban development on natural ecosystems," lead researcher Philipp Sprau said in a news release. "Although we have quantified various environmental parameters, no clear patterns were found which can explain the differences in reproductive success."

Previous research has shown city birds are more clever and aggressive than their rural peers.

The latest great tit study was published this week in the journal Behavioral Ecology.