The British Trust for Ornithology
BARN OWL
Tyto alba

Barn Owl © Colin Varndell
Conservation Listings

Table 4/Amber (25-50% Distribution decline)
Biodiversity Steering Group Conservation Concern List
Long term trend
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 21% to 6% 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
(yrs)		 Years Mean
annual
sample		 Trend Predicted
in first year		 Predicted
in last year		 Change Comment
Clutch size 31 1968-1999 13 Linear increase 4.5 eggs 5.07 eggs 0.57 eggs Small sample
Brood size 31 1968-1999 65 None        
Daily failure rate (eggs) 31 1968-1999 12 Linear decline 0.0069 nests/day 0.0018 nests/day -0.0051 nests/day Small sample
Daily failure rate (chicks) 31 1968-1999 40 Linear decline 0.0023 nests/day 0.0003 nests/day -0.002 nests/day  

Insufficient data on laying date
available for this species

 

Insufficient data on CES
available for this species

 




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This report should be cited as:
Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Beaven, L.P., Downie, I.S., Freeman, S.N., Leech, D.I., Marchant, J.H.,
Noble, D.G., Raven, M.J., Simpkin, A.P., Thewlis, R.M. and Wernham, C.V. (2002) Breeding Birds in the Wider
Countryside: their conservation status 2001. BTO Research Report No. 278. BTO, Thetford. (http://www.bto.org/birdtrends)

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