Tawny Owls Survey 2005

Background

In 1989 the BTO set up the first, and so far only survey of Tawny Owls breeding in Britain. The 1989 survey was set up to investigate factors affecting owl populations in Britain, and to establish a baseline database for their future monitoring. The results formed the basis of BTO Research Report No. 57 (Percival, 1990), on which these present instructions are based.

Owing to their nocturnal habits and sedentary and secretive nature, the population status of the Tawny Owl is relatively poorly known. Traditional BTO monitoring schemes, usually carried out during the morning, do not cover this species well. Results from the Common Birds Census up to the early 1990s show a stable trend, although information from the Breeding Bird Survey shows a 38% decline between 1994 and 2004. Changes between the two Breeding Atlases showed some evidence for a contraction of the species’ UK range. Fieldwork for the New Breeding Atlas was completed in 1991 so we have no up-to-date picture of their distribution since then. Detailed information collected through the Nest Record Scheme shows substantial improvements in nest success during the 30-day egg stage and this could be linked to the declining impact of organochlorine pesticides.

1989 Survey

For some species we need to develop special survey methods in order to get a more accurate picture of their population levels. In 1989 a Tawny Owl Survey was designed and carried out that involved a single 10-minute point count in the centre of randomly selected tetrads (2km x 2km squares) between mid-August and mid-October. This aim of the survey was to collect information on numbers to provide baseline information for future monitoring and to look at densities of owls in different area and habitats.

2005 Survey

In 2005 we launched Tawny Owl Survey and recruited volunteers to help. Volunteers re-visited all the tetrads covered in 1989 and recorded the number of Tawny Owls heard. A single 10 minute count was required in each tetrad from a location as close as possible to the centre of the tetrad (using available roads and footpaths). We then compared the counts with those from 1989 and wrote up the results in BTO News.

All your records of Tawny Owl from throughout the year can be entered onto BirdTrack (www.birdtrack.net) where they will contribute to our knowledge of distribution.

Further reading about Tawny Owls
For further information about Tawny Owls visit the Wider Countryside Report (http://www.bto.org/birdtrends/wcrtawow.htm) and BirdFacts (http://blx1.bto.org/birdfacts/results/bob7610.htm).

References
Percival, S.M. (1990) Population trends in British Barn Owls, Tyto alba, and Tawny Owls, Strix aluco, in relation to environmental change. Research Report 57. BTO, Tring.

The forms used in the survey are listed below for reference:

Tawny Owl Instructions (Word doc)
Tawny Owl Instructions (.pdf file)
Tawny Owl Record Form (Word doc)
Tawny Owl Record Form (.pdf file)
Grid overlay (Word doc)
Grid Overlay (.pdf file)