BOMP

Methodology

The ecology of the Barn Owl - an elusive, predominantly nocturnal species which is found at low densities, does not sing and calls relatively infrequently - means that the species is most easily surveyed by monitoring their potential nest sites each year. Visits to nests during the breeding season also enable recorders to provide information on Barn Owl productivity. Licensed ringers can ring both adults and young birds, thereby enabling dispersal and annual survival to be monitored as well.

a) Key information gathered for BOMP

Site Details

• Information about the type of nest site, box design and siting information. Different types of nest site may influence the success of birds breeding at the site.
• Details of the location of the site (eg six-figure grid reference, held in the strictest confidence). Breeding success may vary geographically due to a range of factors including weather conditions and road densities.
• Information on the habitat types around the nest site and other important features that are present (ditches, railway embankments etc). Breeding success is likely to be influenced by food availability. Different habitats around the nest site may support different numbers of favoured prey species.

Nest Contents

The timing of visits to the nest site and the status/counts of any eggs/young present are being recorded.

b) Submitting BOMP data

BOMP uses Nest Record Scheme methodology to record the location, timing and productivity of Barn Owl nesting attempts. Ideally, nests are visited on two or more occasions and the contents recorded on standard BTO nest record cards or using the home computer inputting program IPMR (Integrated Population Monitoring Reporter).

IPMR Screenshot for a Barn Owl nest	Nest record card for a Barn Owl nest

"Nil Returns" are an essential part of BOMP, as these enable us to work out occupancy rates. Recorders are asked to let us know if a registered BOMP site is not used for nesting or roosting during the season by filling in a separate BOMP form.

Observers are also being asked to record the presence of other species in Barn Owl nest sites (eg Kestrel, Tawny Owl, Little Owl, Jackdaw and Stock Dove) on this form and to quantify the main habitat types in the surrounding area.

c) What can we calculate from the data collected?

Site Occupancy

Details on whether the site is occupied in a given year and by what species. Site occupancy provides a minimum estimate of the number of Barn Owls within an area. If occupancy declines substantially between years, then this may provide an early warning that abundance might be changing.

Measures of Productivity Clutch size Hatching success Occurrence of second broods and replacement clutches Brood size Laying, hatching and fledging dates Presence of stored prey at the nest site

Barn Owl eggs hatch asynchronously. As a result the chicks in a nest may vary in size. These two nestlings have been removed temporarily from a nestbox for ringing.

d) Registering new sites

We are still interested in increasing the coverage of BOMP and would be very pleased to hear from anybody that would like to register new sites for the project. In order to take part you need to know the precise location of the nest site or potential nest site and be able to visit it on several occasions each year to record the information detailed above. If you are interested in registering sites for BOMP then please email us ( ) or phone us on 01842 750050.

It is important to remember that Barn Owls are listed on Schedule 1 of the Wildlife & Countryside Act 1981 and a Schedule 1 Licence must therefore be obtained before approaching any nest site. For more information about obtaining such a licence, please contact the Licensing Officer (email: ) at the BTO.

Next - Results for 2005