The British Trust for Ornithology
WREN
Troglodytes troglodytes
Wren © Tommy Holden
 
Conservation listings

Unlisted/Green
Biodiversity Steering Group: Unlisted
  Long-term trend
UK: Fluctuating after a rapid increase
 
Status summary
Following a rapid increase into the mid-1970s, Wren abundance has fluctuated, chiefly because of the effects of colder and milder winters (Peach et al. 1995b). Abundance, as shown by smoothed CBC trends, has been relatively stable over the last decade, but the BBS and CES reveal large and significant inter-annual fluctuations. Trends in most aspects of breeding performance have tended to improve in the long term. However, the decline in egg-stage failures (from 29% to 22%) is approximately counterbalanced by the increase in chick-stage failures (from 15% to 23%). The long-term trend towards earlier laying is explained by recent climatic warming (Crick & Sparks 1999).
 
 
Table of population changes for Wren
Source Period
(yrs)		 Years Plots
(n)		 Change
(%)		 Lower
limit		 Upper
limit		 Alert Comment
CBC all habitats 31 1968-1999 220 67 45 88    
  25 1974-1999 228 -5 -17 7    
  10 1989-1999 215 6 -1 12    
  5 1994-1999 220 6 1 10    
CBC farmland 31 1968-1999 93 82 62 102    
  25 1974-1999 93 -5 -14 5    
  10 1989-1999 94 11 3 19    
  5 1994-1999 95 12 5 18    
CBC woodland 31 1968-1999 86 33 5 60    
  25 1974-1999 93 -12 -28 4    
  10 1989-1999 98 1 -8 9    
  5 1994-1999 101 2 -4 9    
CES adults 15 1984-1999 94 33 . .    
  10 1989-1999 109 3 . .    
  5 1994-1999 117 -2 . .    
CES juveniles 15 1984-1999 92 44 . .    
  10 1989-1999 108 0 . .    
  5 1994-1999 115 -1 . .    
BBS UK 6 1994-2000 1764 24 20 28    
BBS England 6 1994-2000 1375 11 8 14    
BBS Scotland 6 1994-2000 178 87 62 116    
BBS Wales 6 1994-2000 144 13 2 24    
BBS N.Ireland 6 1994-2000 57 96 52 151    
The Breeding Bird Survey is jointly funded by BTO, JNCC and RSPB
 

 
Table of productivity information for Wren
Variable Period
(yrs)		 Years Mean
annual
sample		 Trend Predicted
in first year		 Predicted
in last year		 Change Comment
Clutch size 31 1968-1999 101 Linear increase 5.58 eggs 5.88 eggs 0.3 eggs  
Brood size 31 1968-1999 129 Curvilinear 3.79 chicks 4.88 chicks 1.09 chicks  
Daily failure rate (eggs) 31 1968-1999 149 Curvilinear 0.0171 nests/day 0.0125 nests/day -0.0046 nests/day  
Daily failure rate (chicks) 31 1968-1999 103 Curvilinear 0.0092 nests/day 0.0144 nests/day 0.0052 nests/day  
Laying date 31 1968-1999 91 Curvilinear day 133 day 125 -8 days  
Percentage juveniles (CES) 15 1984-1999 98 Smoothed trend 90 productivity index 100 productivity index 11%  
Percentage juveniles (CES) 10 1989-1999 114 Smoothed trend 106 productivity index 100 productivity index -6%  
Percentage juveniles (CES) 5 1994-1999 120 Smoothed trend 101 productivity index 100 productivity index -1%  
 




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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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