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BTO Blueline
Strix aluco
Tawny Owl © Tommy Holden
Conservation listings

Europe: SPEC category 4, secure
UK: Green

Long-term trend
UK: stable
Status summary
As a nocturnal species, Tawny Owl is relatively poorly covered by the BTO's monitoring schemes. The pattern shown by CBC/BBS is a remarkably stable one, however, in keeping with the longevity, sedentary behaviour, and slow breeding rate of this species. There is a slight indication of very shallow downward trend since the early 1970s, which recent BBS data, for England and for the UK as a whole, suggest has accelerated since 1999. It may be relevant to this possible long-term change that Gibbons et al. (1993) found evidence for a contraction of the species' UK range between the two atlas periods. The substantial improvements in nest success during the c.29-day egg stage could be linked to the declining impact of organochlorine pesticides.
Table of population changes for Tawny Owl
Source Period
Years Plots
Alert Comment
CBC/BBS UK 33 1967-2000 74 10 -32 59    
  25 1975-2000 84 -12 -33 9    
  10 1990-2000 106 -3 -18 18    
  5 1995-2000 134 -2 -16 11    
CBC/BBS England 33 1967-2000 62 8 -26 62    
  25 1975-2000 70 -9 -26 12    
  10 1990-2000 90 -2 -17 21    
  5 1995-2000 112 1 -12 17    
BBS UK 8 1994-2002 77 -35 -52 -13 (>25)  
BBS England 8 1994-2002 63 -20 -42 10    
BBS acknowledgement
CBC/BBS England graph
BBS UK graph
BBS England graph
Table of productivity information for Tawny Owl
Variable Period
Years Mean
Trend Predicted
in first year
in last year
Change Comment
Clutch size 33 1968-2001 77 None        
Brood size 33 1968-2001 132 None        
Daily failure rate (eggs) 33 1968-2001 53 Linear decline 0.0099 nests/day 0.0021 nests/day -0.0078 nests/day  
Daily failure rate (chicks) 33 1968-2001 79 None        
Laying date 33 1968-2001 13 None       Small sample
Clutch size graph
Brood size graph
Egg nest failure graph
Chick nest failure graph
Laying date graph
Insufficient data on CES
available for this species
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This report should be cited as:
Crick, H.Q.P., Marchant, J.H., Noble, D.G., Baillie, S.R., Balmer, D.E., Beaven, L.P., Coombes, R.H.,
Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. and Thewlis, R.M. (2004)
Breeding Birds in the Wider Countryside: their conservation status 2003.
BTO Research Report No. 353. BTO, Thetford. (http://www.bto.org/birdtrends2003)

Pages maintained by Susan Waghorn and Iain Downie: Last updated 16 February, 2009