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Breeding Bird Survey
Common Birds Census
Constant Effort Sites
Nest Record Scheme
Waterways Bird Survey
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WREN Troglodytes troglodytes
 
Conservation Listings Long term trend

Unlisted/Green
Biodiversity Steering Group: Unlisted

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 23%) is approximately counter-balanced by the increase in chick-stage failures (from 15% to 23%). The long-term trend towards earlier laying is explained by recent climate 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 30 1968-1998 220 50 31 68    
  25 1973-1998 227 -9 -20 0    
  10 1988-1998 214 2 -3 8    
  5 1993-1998 222 -6 -10 -2    
CBC farmland 30 1968-1998 93 55 . .    
  25 1973-1998 93 -13 . .    
  10 1988-1998 93 4 . .    
  5 1993-1998 95 -5 . .    
CBC woodland 30 1968-1998 86 23 . .    
  25 1973-1998 92 -14 . .    
  10 1988-1998 97 0 . .    
  5 1993-1998 102 -6 . .    
CES adults 14 1984-1998 91 37 . .    
  10 1988-1998 105 10 . .    
  5 1993-1998 114 -2 . .    
CES juveniles 14 1984-1998 90 38 . .    
  10 1988-1998 103 5 . .    
  5 1993-1998 113 -4 . .    
BBS UK 5 1994-1999 1698 17 13 21    
BBS England 5 1994-1999 1327 10 7 14    
BBS Scotland 5 1994-1999 175 60 39 85    
BBS Wales 5 1994-1999 132 15 3 27    
BBS N.Ireland 5 1994-1999 53 48 12 95    
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 30 1968-1998 101 Curvilinear 5.64 eggs 6 eggs 0.36 eggs  
Brood size 30 1968-1998 127 Curvilinear 3.82 chicks 4.92 chicks 1.1 chicks  
Daily failure rate (eggs) 30 1968-1998 149 Curvilinear 0.0171 nests/day 0.0129 nests/day -0.0042 nests/day  
Daily failure rate (chicks) 30 1968-1998 102 Curvilinear 0.0094 nests/day 0.0154 nests/day 0.006 nests/day  
Laying date 30 1968-1998 92 Curvilinear day 133 day 126 -7 days  
Percentage juveniles (CES) 14 1984-1998 96 Smoothed trend 96 productivity index 100 productivity index 4%  
Percentage juveniles (CES) 10 1988-1998 109 Smoothed trend 108 productivity index 100 productivity index -8%  
Percentage juveniles (CES) 5 1993-1998 117 Smoothed trend 104 productivity index 100 productivity index -4%  
 
   



The report should be cited as: Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Bashford, R.I., Beaven, L.P., Freeman, S.N., Marchant, J.H., Noble, D.G., Raven, M.J., Siriwardena, G.M., Thewlis, R. and Wernham, C.V. (2001) Breeding Birds in the Wider Countryside: their conservation status 2000. BTO Research Report No. 252. BTO, Thetford. (http://www.bto.org/birdtrends)

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