Contents of report
Breeding Bird Survey
Common Birds Census
Constant Effort Sites
Nest Record Scheme
Waterways Bird Survey
What the categories mean
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BARN OWL Tyto alba
Conservation Listings Long term trend

Table 4/Amber
(25-50% Distribution decline)
Biodiversity Steering Group
Conservation Concern List

UK: Uncertain

Status Summary
Productivity has tended to improve since the 1950s and 1960s when Barn Owls appear to have been affected by organochlorine pesticides (Percival 1990). In addition to an increase in clutch size, nest failure rates have fallen at the egg stage (34 days) from 20% to 7% and at the nestling stage (60 days) from 13% to 2%. A national census, organised jointly by Hawk & Owl Trust and BTO 1995-97, has provided a replicable baseline estimate of population size of c.4000 breeding pairs in the UK (Toms et al. 2001), but population trends are currently not monitored annually.
Annual breeding population changes for this species
are not currently monitored by BTO
Table of productivity information for Barn Owl
Variable Period
Years Mean
Trend Predicted
in first year
in last year
Change Comment
Clutch size 30 1968-1998 13 Linear increase 4.48 eggs 5.09 eggs 0.61 eggs Small sample
Brood size 30 1968-1998 63 None        
Daily failure rate (eggs) 30 1968-1998 11 Linear decline 0.0066 nests/day 0.0021 nests/day -0.0045 nests/day Small sample
Daily failure rate (chicks) 30 1968-1998 38 Linear decline 0.0024 nests/day 0.0003 nests/day -0.0021 nests/day  

Insufficient data on laying date
available for this species


Insufficient data on CES
available for this species



The report should be cited as: Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Bashford, R.I., Beaven, L.P., Freeman, S.N., Marchant, J.H., Noble, D.G., Raven, M.J., Siriwardena, G.M., Thewlis, R. and Wernham, C.V. (2001) Breeding Birds in the Wider Countryside: their conservation status 2000. BTO Research Report No. 252. BTO, Thetford. (

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