City birds 'cope better in cold' than those in woodland

Blue tit feeding on nuts in garden
Image caption "Urban scavenger" birds rely less on one source of food such as caterpillars

Urban breeding birds fared better than their woodland counterparts during 2012's cold, wet weather for the first time in 10 years, a study has found.

Blue and great tits in a woodland area were compared with those in Cambridge.

Researchers found urban birds relied less on a single source of food, such as caterpillars, whose numbers are affected by cold weather.

Woodland birds also bred less during the cold spell in 2012, said the Anglia Ruskin University study.

It was carried out in conjunction with the Centre for Ecology and Hydrology (CEH).

The British Trust for Ornithology (BTO) referred to 2012 as "one of the worst breeding seasons on record" following poor results in its annual surveys of nests and fledglings.

'Urban advantage'

The latest study concluded birds living in native British woodland were "more susceptible to the effects of extreme weather conditions than those in urban environments".

Birds at Brampton Wood nature reserve - a traditional British woodland - typically "fared significantly better" in the past, and bred more successfully than those studied at Cambridge University Botanic Garden in the centre of Cambridge.

However, for the first time in the 10 years their breeding habits have been monitored, those at Brampton laid fewer eggs and hatched and fledged fewer chicks than those in the city.

The chicks in Brampton also took almost twice as long to hatch as those in the Botanic Garden nests - 32 days as opposed to 17.

Anglia Ruskin's Dr Nancy Harrison described the hatching delay as "unprecedented" during the study period.

The cold weather played a "key role" in caterpillar reproduction and growth, reducing numbers and in turn reducing the main food source for the woodland birds, she said.

"Urban scavenger" blue and great tits living in towns were used to foraging for other prey, so were not as adversely affected by a shortage of caterpillars, Dr Harrison added.

"If these extreme weather events become more commonplace [as a result of] the effects of climate change, then birds living in urban environments may have the advantage," she said.

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