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BTO Blueline
SEDGE WARBLER
Acrocephalus schoenobaenus
Sedge Warbler © Tommy Holden
Conservation listings

Europe: SPEC category 4, (secure)
UK: Green

Long-term trend
UK: fluctuating, with no long-term trend
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 Sahel (trans-Saharan) wintering grounds (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 last three of the same troughs and also illustrates the large year-to-year fluctuations that occur in this species. No strong trends are apparent in breeding performance, but CES productivity has shown a steady decline since 1983.
 
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 33 1967-2000 94 -12 -46 17    
  25 1975-2000 109 34 4 73    
  10 1990-2000 192 19 5 44    
  5 1995-2000 295 25 12 40    
CBC/BBS England 33 1967-2000 66 -25 -60 6    
  25 1975-2000 75 12 -16 36    
  10 1990-2000 126 6 -7 31    
  5 1995-2000 190 12 1 28    
WBS waterways 25 1975-2000 44 -15 -41 33    
  10 1990-2000 55 -10 -23 5    
  5 1995-2000 58 -4 -15 9    
CES adults 17 1984-2001 63 -9 . .    
  10 1991-2001 77 -20 . .    
  5 1996-2001 82 -18 . .    
CES juveniles 17 1984-2001 60 -37 . . [>25*]  
  10 1991-2001 73 -43 . . [>25*]  
  5 1996-2001 77 -28 . . [>25*]  
BBS UK 8 1994-2002 242 30 14 48    
BBS England 8 1994-2002 153 32 12 55    
BBS Scotland 8 1994-2002 47 53 11 110    
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
 
Table of productivity information
Variable Period
(yrs)
Years Mean
annual
sample
Trend Predicted
in first year
Predicted
in last year
Change Comment
Clutch size 33 1968-2001 40 Curvilinear 4.94 eggs 4.89 eggs -0.05 eggs  
Brood size 33 1968-2001 63 None        
Daily failure rate (eggs) 33 1968-2001 47 Linear decline 0.0132 nests/day 0.0071 nests/day -0.0061 nests/day  
Daily failure rate (chicks) 33 1968-2001 54 None        
Laying date 33 1968-2001 54 None        
Percentage juveniles (CES) 17 1984-2001 68 Smoothed trend 171 productivity index 101 productivity index -41%[>25]  
Percentage juveniles (CES) 10 1991-2001 83 Smoothed trend 148 productivity index 101 productivity index -32%[>25*]  
Percentage juveniles (CES) 5 1996-2001 87 Smoothed trend 122 productivity index 101 productivity index -18%  
 
Clutch size graph
Brood size graph
Egg nest failure graph
Chick nest failure graph
Laying date graph
CES productivity graph
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This report should be cited as:
Crick, H.Q.P., Marchant, J.H., Noble, D.G., Baillie, S.R., Balmer, D.E., Beaven, L.P., 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. (2004)
Breeding Birds in the Wider Countryside: their conservation status 2003.
BTO Research Report No. 353. BTO, Thetford. (http://www.bto.org/birdtrends2003)

Pages maintained by Susan Waghorn and Iain Downie: Last updated 16 February, 2009