BTO - Breeding Birds of the Wider Countryside: Wren

WREN
Troglodytes troglodytes

• Population
changes

• Productivity
trends

• Additional
information

Conservation listings

Europe: no SPEC category (favourable conservation status in Europe, not concentrated in Europe)
UK: green
UK Biodiversity Action Plan (Fair Isle & St Kilda races only): in preparation

Long-term trend

UK, England: moderate increase

UK population size

8,512,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)

Status summary

The Wren's current UK population estimate is the highest for any species. Abundance can vary sharply from year to year in this species, as is evident from the unsmoothed trends presented here for BBS. Annual numbers are influenced by mortality rates that may be very high in severe winters and by the species' high breeding potential (Peach et al. 1995b). Wren numbers in the UK were greatly depleted by the cold winter of 1962/63 (Marchant et al. 1990). Following a rapid recovery up to the mid 1970s, abundance fell again in response to a further series of cold winters only to return to its previous high level. BBS results suggest that increase since 1994 has been much stronger in Scotland and Northern Ireland than in Wales and England. Brood size appears to have shown a small improvement in the long term, and fewer nests are now failing at the egg stage. Numbers have risen widely in Europe since 1980 (PECBM 2006).

Population changes

Table of population changes for Wren

Source	Period (yrs)	Years	Plots (n)	Change (%)	Lower limit	Upper limit
CBC/BBS UK	38	1967-2005	762	95	69	120
	25	1980-2005	1048	50	35	59
	10	1995-2005	2147	20	16	24
	5	2000-2005	2256	1	-2	3
CBC/BBS England	38	1967-2005	607	88	58	115
	25	1980-2005	826	42	25	53
	10	1995-2005	1674	14	9	17
	5	2000-2005	1738	-1	-4	1
CES adults	21	1984-2005	95	55	30	84
	10	1995-2005	109	14	4	26
	5	2000-2005	102	2	-6	11
CES juveniles	21	1984-2005	94	31	6	59
	10	1995-2005	108	3	-6	16
	5	2000-2005	102	-12	-20	-4
BBS UK	10	1995-2005	2023	21	16	24
	5	2000-2005	2224	2	-1	4
BBS England	10	1995-2005	1566	13	8	16
	5	2000-2005	1710	1	-2	3
BBS Scotland	10	1995-2005	188	62	41	81
	5	2000-2005	191	9	0	18
BBS Wales	10	1995-2005	179	17	3	24
	5	2000-2005	214	1	-4	6
BBS N.Ireland	10	1995-2005	79	54	20	91
	5	2000-2005	97	-2	-10	7

BBS N Ireland graph

Productivity trends

Table of productivity changes for Wren

Variable	Period (yrs)	Years	Mean annual sample	Trend	Modelled in first year	Modelled in 2005	Change
Clutch size	37	1968-2005	94	None
Brood size	37	1968-2005	94	None
Daily failure rate (eggs)	37	1968-2005	141	Linear decline	1.84% nests/day	1.43% nests/day	-22.3%
Daily failure rate (chicks)	37	1968-2005	97	None
Laying date	37	1968-2005	87	Linear decline	May 14	May 9	-5 days
Juvenile to Adult ratio (CES)	21	1984-2005	99	Smoothed trend	109 Index value	100 Index value	-8%
Juvenile to Adult ratio (CES)	10	1995-2005	111	Smoothed trend	107 Index value	100 Index value	-7%
Juvenile to Adult ratio (CES)	5	2000-2005	105	Smoothed trend	113 Index value	100 Index value	-12%

Additional information


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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., Barimore, C., Coombes, R.H., Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. & Thewlis, R.M. (2007) Breeding Birds in the Wider Countryside: their conservation status 2007. BTO Research Report No. 487. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Susan Waghorn and Iain Downie: Last updated 3 January, 2008