Wading birds decline not down to ravens

Ravens are not to blame for a dramatic drop in the numbers of wading birds seen in parts of the UK, a study said yesterday.

Although wading bird numbers in upland areas had decreased and ravens had increased in some parts, there was little evidence to suggest they caused the decline, researchers said.

The number of wading birds such as curlew, lapwing and dunlin have declined by at least 50 per cent in the past 25 years, previous RSPB research has shown.

In the study, RSPB data from sites across more than 1,700 sq km of the uplands were analysed to see the patterns of change in the number of ravens and waders in the past 20 years.

The RSPB and the University of Aberdeen's Centre for Environmental Sustainability study found "weak associations" between increases in ravens and declines in lapwing and curlew but the relationships were not statistically significant, and may have been the result of chance.

There were also no relationships between the rise in ravens and the decline in snipe, golden plover and dunlin in upland areas which include Exmoor in Somerset, the Highlands in Scotland and the Lake District in Cumbria.

Prof. Steve Redpath, director of Aces, said: "We urgently need to understand why upland wader populations are suffering dramatic declines across many parts of the UK. It is often the case that predators are assumed to be responsible, but this is not always the case.

"This research found no strong evidence to suggest that ravens were responsible for changes in wader numbers, implying that we need to look elsewhere to discover the cause for these large-scale declines."

The research suggests other factors, including changes to habitat and vegetation cover and a general increase in other predators such as foxes, could be responsible for the decline in wading bird numbers.

Arjun Amar, a senior conservation scientist with RSPB, who led the study, said: "In the past 20 years ravens have undergone a welcome recovery.

"While many organisations view these changes as positive, increases in raven numbers have raised legitimate concerns among other groups, because of their perceived impact on prey species, and this can lead to conflict between land managers and conservation organisations.

"We hope that this new research will help the licensing authorities balance the need to safeguard populations of vulnerable, recovering predators, whilst at the same time acknowledging and addressing concerns over increasing predator populations.

"These decisions need to be informed by the best evidence, in particular the impact that predators are having on prey populations."

Dr Amar said the research followed applications for licences in Scotland to kill ravens to protect upland birds.

He said: "Ravens are known to eat the eggs and chicks of upland waders, however, this does not necessarily mean that they will cause the decline of these prey species and this study demonstrates that it is very unlikely that ravens were the cause of the population decline."

The research was funded by Scottish Natural Heritage, the RSPB and Aces.

Andrew Douse, ornithologist with SNH, said: "As the relevant licensing authority, SNH needs to base its decisions on good evidence.

"We will use the findings of this work and related studies to help inform our decisions.

"We are keen to see these findings made more widely available, not least in order to help inform licence applications."

The Breeding Bird Survey found that from 1994 to 2007 the raven population increased in the UK by 134 per cent.