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Climate Change Link to Ouzel Decline?

Food shortages make for poor condition on migration?

Pioneering research work undertaken by the RSPB (BirdLife in the UK) has shown that a sharp decline in the numbers of one of the UK’s least understood birds could be linked to climate change. Now conservation scientists from RSPB Scotland are to monitor the movements of the Ring Ouzel Turdus torquatus using radio-tracking equipment, in the hope that the study will provide information to help them improve the status of the species. The species is in serious trouble in the UK with an estimated population decline of almost 60% between 1990 and 1999.

The climate change research work published in the Journal of Animal Ecology reveals that the drop in the ouzel’s population could be linked to recent increases in UK temperatures in July and August after most chicks have fledged.

One theory is that warmer weather has affected the species’ food supplies in late summer, perhaps drying the ground and reducing the availability of earthworms, or else affecting berry crops on moorlands. This shortage of staple food supplies may in turn affect the condition of adult and young birds as they prepare to return to their wintering grounds in Morocco."Changes in climate are perhaps affecting what is available for them to eat – most notably earthworms and other likely staples such as bilberries – leaving them in a poor condition to migrate in September." said Dr Colin Beale who led the research, he further commented: "The drop in Ring Ouzel numbers is not caused by reduced nesting success by the birds – in fact this has increased as the population has declined. Instead, it seems that the problems begin after the breeding season when the chicks have fledged. Changes in climate are perhaps affecting what is available for them to eat – most notably earthworms and other likely staples such as bilberries – leaving them in a poor condition to migrate in September. These are the ideas that the new research is set to test."

Very little is known about what the birds do in the period after they finish breeding in the UK and before they migrate south for the winter. It is during this period that a number of Scottish birds – around 25 or so in the Highlands – will be fitted with radio tags and their movements tracked using radio receivers to monitor each bird’s individual behaviour.The Ring Ouzel is one of the UK’s least studied and most poorly understood birds, which is why our research into the problems it’s experiencing is so vital, said Dr Jeremy Wilson, Head of Research for RSPB Scotland. We’re now hoping that this tagging project will help us find out more about what these birds feed on, what habitats they use and how far they disperse from their breeding areas before they migrate. The findings could be crucial in helping to manage upland areas better for ouzels – and protect them from the impacts of climate change in the future.

The RSPB also helped to establish the Ring Ouzel Study Group in 1998 – visit http://www.ringouzel.info

4th July 2014