Cold comfort

 
By Ragini Letitia Singh
Last Updated: Saturday 04 July 2015 | 02:50:09 AM

Rising temperatures push North American birds to the far north

BIRDS usually fly south to warmer regions in winter. But birds in North America were found moving north to colder climes in early winter. Audubon Society, a leading US-based advocacy group for conserving wildlife and ecology, reported this unusual change in migratory patterns in February 2009 after a study over four decades.

More than half the 305 bird species in North America including robins, gulls and owls were found spending winters farther north during the Society's annual Christmas bird count. Most of the 177 species moved an average 55 km north. But 60 species moved in excess of 160 km north. The purple finch was found spending its winter more than 600 km farther north.

Food security and a safe place to breed are the usual reasons why birds migrate to warmer regions. In this instance, their movement pattern towards the colder northern region, is attributed to climate change. The temperature in January, which used to be the coldest month in America, rose by 2.7C in the past 40 years.

This steady rise in temperature has coincided with the northward movement of the birds. The observations were recorded over long periods by citizen-scientists and backed by scientific data and analysis by the Audubon Society.

"These findings show very clearly that warming temperatures have profound effects on the natural world. Many effects of climate change are expected, including on the seasonal timing of biological events like migration and reproduction," said Suhel Quader, researcher at the National Centre for Biological Sciences, Bengaluru. Quader is also coordinator of Migrant Watch, the first large-scale effort in India by citizen-scientists to monitor the impact of climate change on wild species.

The Audubon Society study adds to previous observations about climate change affecting bird migration. The geographical distribution of many animal and plant species is shifting progressively towards the poles or up the mountains as the earth becomes warmer.

The strongest impact are on species that live in temperate regions. Not much is known about what is happening in the tropics as studies have not been published on climate related behaviour change in birds and animals.

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