BTO - Breeding Birds of the Wider Countryside: Tawny Owl

TAWNY OWL
Strix aluco

Conservation listings

Europe: no SPEC category (concentrated in Europe, conservation status favourable)
UK: green

Long-term trend

UK, England: fluctuating, with no long-term trend

Distribution maps

Maps and statistics from British and Irish
atlases can be viewed here.

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 relatively 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 (yrs)	Years	Plots (n)	Change (%)	Lower limit	Upper limit	Alert	Comment
CBC/BBS UK	35	1967-2002	74	-7	-38	33
	25	1977-2002	85	-24	-42	-1
	10	1992-2002	111	-18	-34	1
	5	1997-2002	125	-19	-33	-3
CBC/BBS England	35	1967-2002	62	4	-30	61
	25	1977-2002	71	-8	-35	26
	10	1992-2002	94	-6	-26	17
	5	1997-2002	106	-5	-24	18
BBS UK	9	1994-2003	76	-32	-49	-10	(>25)	Nocturnal species
BBS England	9	1994-2003	63	-1	-27	33		Nocturnal species

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 34 1968-2002 76 None

Brood size 34 1968-2002 131 None

Daily failure rate (eggs) 34 1968-2002 52 Linear decline 0.0099 nests/day 0.0019 nests/day -0.008 nests/day

Daily failure rate (chicks) 34 1968-2002 78 None

Laying date 34 1968-2002 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., Marchant, J.H., Crick, H.Q.P., Noble, D.G., 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. (2005) Breeding Birds in the Wider Countryside: their conservation status 2004. BTO Research Report No. 385. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Susan Waghorn and Iain Downie: Last updated 18 January, 2006