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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: fluctuating, with no long-term trend
UK population size
321,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)
Status summary
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 and also illustrates the large year-to-year fluctuations that occur in this species. Daily nest failure rates at the egg stage have almost halved. CES productivity data show a steep fall in the 1980s, followed by further shallow decrease.
 

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 England 36 1967-2003 71 -24 -62 12    
  25 1978-2003 85 -2 -27 22    
  10 1993-2003 163 25 4 54    
  5 1998-2003 182 12 -3 29    
CBC/BBS UK 36 1967-2003 103 -22 -55 10    
  25 1978-2003 127 1 -22 47    
  10 1993-2003 252 22 9 47    
  5 1998-2003 286 1 -8 13    
WBS waterways 28 1975-2003 43 -10 -39 42    
  25 1978-2003 44 -17 -39 19    
  10 1993-2003 51 7 -14 31    
  5 1998-2003 45 7 -8 26    
CES adults 19 1984-2003 63 -11 -38 12    
  10 1993-2003 77 -8 -21 6    
  5 1998-2003 74 -6 -14 2    
CES juveniles 19 1984-2003 60 -29 -45 -5 >25  
  10 1993-2003 74 -21 -39 -4    
  5 1998-2003 71 1 -15 22    
BBS UK 10 1994-2004 248 15 2 31    
BBS England 10 1994-2004 158 31 13 53    
BBS Scotland 10 1994-2004 47 -1 -29 36    

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 2003
Change Comment
Clutch size 35 1968-2003 39 Curvilinear 4.95 eggs 4.88 eggs -1.3%  
Brood size 35 1968-2003 61 None        
Daily failure rate (eggs) 35 1968-2003 46 Linear decline 1.28% nests/day 0.67% nests/day -47.7%  
Daily failure rate (chicks) 35 1968-2003 52 None        
Laying date 35 1968-2003 52 None        
Juvenile to Adult ratio (CES) 19 1984-2003 68 Smoothed trend 218 Index value 103 Index value -54% >50  
Juvenile to Adult ratio (CES) 10 1993-2003 83 Smoothed trend 122 Index value 103 Index value -18%  
Juvenile to Adult ratio (CES) 5 1998-2003 81 Smoothed trend 97 Index value 103 Index value 3%  

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

Additional information

BTO blue divider
 

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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., 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. (2006)
Breeding Birds in the Wider Countryside: their conservation status 2005.
BTO Research Report No. 435. BTO, Thetford. (http://www.bto.org/birdtrends)

Pages maintained by Susan Waghorn and Iain Downie: Last updated 11 November, 2008