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BTO Blueline
SEDGE WARBLER
Acrocephalus schoenobaenus
Sedge Warbler © Tommy Holden
 

• Population
  changes

• Productivity
  trends

• Additional
  information
Conservation listings
Europe: no SPEC category (concentrated in Europe, conservation status favourable)
UK: green
Long-term trend
UK: moderate decline
UK population size
321,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)
Status summary
The trend in England is apparently of moderate decline, but this is uncertain because the long-term changes are partly obscured by shorter fluctuations in numbers. Detailed analysis of BTO data sets has shown that much of the year-to-year variation in population size is driven by changes in adult survival rates which, in turn, are related to changes in rainfall on their wintering grounds, just south of the Sahara Desert, in the West African Sahel (Peach et al. 1991). The smoothed CBC/BBS and WBS trends show four troughs in population, related to years of poor West African rainfall, with a low point in 1984–85. The CES, which provides the biggest Sedge Warbler sample, shows the most recent three of the same troughs. Daily nest failure rates at the egg stage have halved. CES productivity data show a sustained decrease since the late 1980s. Sedge Warblers are estimated to have declined by 65% across Europe during 1980–2005 (PECBMS 2007).
 

Population changes
CBC/BBS UK graph
 
Table of population changes for Sedge Warbler

Source Period
(yrs)		 Years Plots
(n)		 Change
(%)		 Lower
limit		 Upper
limit		 Alert Comment
CBC/BBS UK 39 1967-2006 118 -28 -58 18    
  25 1981-2006 158 2 -20 38    
  10 1996-2006 297 -3 -18 11    
  5 2001-2006 283 -16 -29 -6    
CBC/BBS England 39 1967-2006 81 -39 -69 -13 >25  
  25 1981-2006 104 -10 -31 13    
  10 1996-2006 190 -12 -24 1    
  5 2001-2006 182 -19 -28 -11    
WBS waterways 31 1975-2006 43 -28 -56 24    
  25 1981-2006 46 -25 -47 10    
  10 1996-2006 47 -18 -37 8    
  5 2001-2006 36 -11 -24 4    
CES adults 22 1984-2006 64 -33 -49 -11 >25  
  10 1996-2006 74 -46 -54 -37 >25  
  5 2001-2006 64 -26 -34 -19 >25  
CES juveniles 22 1984-2006 61 -46 -60 -26 >25  
  10 1996-2006 71 -50 -61 -40 >50  
  5 2001-2006 63 -27 -40 -11 >25  
BBS UK 11 1995-2006 270 -1 -17 15    
  10 1996-2006 278 -3 -18 10    
  5 2001-2006 283 -14 -26 -5    
BBS England 11 1995-2006 172 -12 -28 5    
  10 1996-2006 176 -13 -27 4    
  5 2001-2006 182 -16 -25 -6    
BBS Scotland 11 1995-2006 49 15 -19 57    
  10 1996-2006 49 9 -20 44    
  5 2001-2006 46 -14 -35 5    

BBS acknowledgement
 
CBC/BBS England graph
WBS UK graph
CES adult abundance graph
CES juvenile abundance graph
BBS UK graph
BBS England graph
BBS Scotland graph
 

Productivity trends
Table of productivity changes for Sedge Warbler

Variable Period
(yrs)		 Years Mean
annual
sample		 Trend Modelled
in first year		 Modelled
in 2006		 Change Comment
Clutch size 38 1968-2006 37 Curvilinear 4.95 eggs 4.85 eggs -2%  
Brood size 38 1968-2006 57 None        
Daily failure rate (eggs) 38 1968-2006 44 Linear decline 1.3% nests/day 0.61% nests/day -53.1%  
Daily failure rate (chicks) 38 1968-2006 49 None        
Laying date 38 1968-2006 49 Curvilinear May 29 May 23 -6 days  
Juvenile to Adult ratio (CES) 22 1984-2006 69 Smoothed trend 221 Index value 100 Index value -55% >50  
Juvenile to Adult ratio (CES) 10 1996-2006 80 Smoothed trend 121 Index value 100 Index value -17%  
Juvenile to Adult ratio (CES) 5 2001-2006 70 Smoothed trend 101 Index value 100 Index value -1%  

 
Clutch size graph
Brood size graph
Egg nest failure graph
Chick nest failure graph
Laying date graph
CES productivity graph
 

Additional information
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This report should be cited as:
Baillie, S.R., Marchant, J.H., Leech, D.I., Joys, A.C., Noble, D.G.,
Barimore, C., Grantham, M.J., Risely, K. & Robinson, R.A. (2009).
Breeding Birds in the Wider Countryside: their conservation status 2008.
BTO Research Report No. 516. BTO, Thetford. (http://www.bto.org/birdtrends)

Pages maintained by Iain Downie, Mandy T Andrews and Laura Smith: Last updated 18.02.2009