How climate change is affecting British bird populations

Scientists have long understood that climate change is causing the distributions of bird populations to shift. Warmth-loving species such as Dartford Warbler are heading north as temperatures in Britain rise, while cold-adapted mountain birds are heading further uphill.

However, researchers are realising that not all species are reacting to climate change in the same way. One reason may be that individual species respond to subtly different aspects of climate, such as temperature or rainfall, at critical times of the year. Understanding this will help policymakers to adopt conservation and land management strategies that effectively assist species survival.

Scientists at the British Trust for Ornithology (BTO) compared distribution maps for 122 British birds in 1988-91 and 2008-11 to measure the ways in which their breeding distributions have changed. Spring and summer temperatures have increased between these two periods, which should have pushed species to the north-west if this aspect of climate change is key to their success, while higher temperatures in winter should have pushed them to the north and north-east. If spring rainfall is critical to a species, it should have been pushed to the west.

Researchers found that birds had indeed shifted to the north, on average by 8 miles, which continued a trend seen in previous decades. They also found that more than a quarter of species had extended their ranges to the north-west and north-east, and that almost half had retreated from the south.

Simon Gillings, Head of Population Ecology and Modelling and Principal Ecologist said: “We already knew that bird communities might change because some species aren’t moving northwards as fast as others. But if they are also diverging in space, the communities of tomorrow could be very different from those found today.”

The range shifts could not be explained by any single climatic factor, leading researchers to conclude that the distribution changes for British birds are complex, multi-directional and species specific. Some species are apparently adapting to the changing climate, or even benefiting from it. However, others are not and it is not yet clear what impact the arrival of species new to particular areas will have on existing biodiversity. There is still much to learn in order to effectively manage the impacts of anthropogenic climate change on our wildlife.