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Bad weather hits birds’ breeding season

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great_tit

Great tits credit: Dave Leech

Many nesting birds have suffered the worst breeding season on record following the cold and wet weather during the spring and summer.

The number of chaffinch fledglings per nest was at its lowest level since records began in 1966, according to the British Trust for Ornithology’s (BTO) Nest Record Scheme. Blue tits and great tits also produced significantly fewer fledglings, with great tits suffering their second worst breeding season on record.

“Caterpillars appear to have been in short supply during the cold, wet weather and many of the woodland birds dependent on them had a poor season,” said Carl Barimore, Nest Record Scheme Organiser. Problems may also have been caused by eggs and chicks becoming wet and chilled when the female left the nest to search for food.

Dunnocks, nuthatches and sparrows also all produced at least 20% fewer fledglings per nest this year compared to the five-year average.

A shortage of caterpillars and flying insects, along with chilled eggs and chicks in open-cup nests also spelt trouble for migrant warblers. The eight species, including garden warblers, blackcaps and chiffchaffs, monitored by the BTO’s Constant Effort Sites scheme which uses ringing to study the abundance, breeding success and survival of 24 common songbirds, suffered the lowest productivity since the survey began in 1983.

Birds such as blackbirds and robins which feed primarily on soil invertebrates and molluscs fared better in the rainy weather although the number of fledglings produced per nest was still below the five-year average, according to the Nest Record Scheme findings.

“There is no doubt that many fewer young birds fledged this year and current predictions of another cold winter suggest that survival rates over coming months may be low”, said Dr Dave Leech, a Senior Research Ecologist at BTO. “This is likely to have a negative impact on abundance at the start of the 2013 season, but many of the smaller bird species are able to rapidly produce large numbers of young, and so have the potential to bounce back quickly after a single bad year. The worry is that the extreme conditions in 2012 were the result of a shift in the position of the jet stream and it is very difficult to predict how increasing global temperatures and melting of the Arctic ice will influence this in future. If these conditions become more frequent, they could have long-term consequences for Britain and Ireland’s bird populations.”

www.bto.org

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