BTO - Breeding Birds of the Wider Countryside: Tawny Owl

TAWNY OWL
Strix aluco

Conservation Listings

Unlisted/Green
Biodiversity Steering Group Conservation Concern List

Long term trend

UK: Uncertain

Status Summary

As a nocturnal species, Tawny Owl is probably poorly covered by the CBC and the BBS. The non-significant long-term changes shown by both surveys may not, therefore, reflect real trends well. It may be notable that Gibbons et al. (1993) found evidence for a contraction of the species' UK range. The improvements in egg-stage nesting success could be linked to the declining impact of organochlorine pesticides. For the c.29-day egg stage, nest failure rates have fallen, on average, from 26% to 6%.

Table of population changes for Tawny Owl

Source Period
(yrs) Years Plots
(n) Change
(%) Lower
limit Upper
limit Alert Comment

CBC all habitats 31 1968-1999 59 3 -29 41

25 1974-1999 63 -12 -32 11

10 1989-1999 58 -1 -17 15

5 1994-1999 56 0 -14 10

BBS UK 6 1994-2000 77 -8 -31 22

BBS England 6 1994-2000 63 -5 -32 31

The Breeding Bird Survey is jointly funded by BTO, JNCC and RSPB

Table of productivity information for Tawny Owl

Variable Period
(yrs) Years Mean
annual
sample Trend Predicted
in first year Predicted
in last year Change Comment

Clutch size 31 1968-1999 78 None

Brood size 31 1968-1999 133 None

Daily failure rate (eggs) 31 1968-1999 54 Linear decline 0.01 nests/day 0.0023 nests/day -0.0077 nests/day

Daily failure rate (chicks) 31 1968-1999 80 None

Laying date 31 1968-1999 13 None Small sample

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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