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Monthly Archives: October 2011

New Reach for Harrier Roost Survey

Long-running study links in with Natural England project

The long-running Hen Harrier Winter Roost Survey, which the Trust has supported for many years, is extending its reach.

This winter, 2011-12, it will contribute to a Natural England project looking at numbers of roosting hen harriers and merlins at selected Sites of Special Scientific Interest (SSSIs) in southern England.

This follows on from a similar survey conducted by the Hawk and Owl Trust in 2005.

The 2011 work will be jointly co-ordinated and managed by the British Trust for Ornithology and the Hawk and Owl Trust. They will utilise the expert knowledge of existing roost observers and also recruit new volunteers to visit sites not already covered by the Hen Harrier Winter Roost Survey.

It is hoped that this new effort will result in a resurgence of interest and participation in this important survey. Now in its 29th year, it is the only one of its kind for non-breeding raptors in the UK.

It was started by the late Donald Watson with Hawk and Owl Trust accountant and scientific adviser Dr Roger Clarke, who co-ordinated it until his death in 2007. The Trust then joined with the BTO to continue it.

Volunteers record harriers at roosts on six co-ordinated days throughout the winter.

“In a world of agricultural intensification, climate change and persecution, the survey provides an invaluable tool for keeping track of changes in hen harrier numbers in the UK,”

explains Dr Andrew Dobson who carried out a Trust-funded study into hen harriers for his PhD. He is now a research ecologist with the BTO.

“That’s why the BTO and Hawk and Owl Trust are keen to see the survey grow to cover roosts which are not currently part of the survey – and funding from the Natural England project will help make this happen.”

Data from last winter showed up apparent differences in distribution between grey birds (mainly adult males) and brown birds (females and immature males). Proportions of males were higher in South and South West England than in the east (south of Lincolnshire), matching patterns reported in the 1980s and 90s. Counts from the north of England and Wales were too low to interpret, so more data from these regions would be helpful in establishing if this is a countrywide trend. Reasons for such intersexual segregation are currently unclear.

“The survey requires very little in the way of bird ID skills. You just need to find a suitable vantage point near roosting harriers and wait and see,” said Andy.

To volunteer to help this winter and find out what is involved, contact Hawk and Owl Trust conservation officer Nigel Middleton (email here or phone 07867 572794) who is the national Hen Harrier Winter Roost Co-ordinator.