BTO - Breeding Birds of the Wider Countryside: Sedge Warbler

SEDGE WARBLER
Acrocephalus schoenobaenus

Conservation listings

Europe: no SPEC category (concentrated in Europe, conservation status favourable)
UK: green

Long-term trend

UK: fluctuating, with no long-term trend

Distribution maps

Maps and statistics from British and Irish
atlases can be viewed here.

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 the late 1980s.

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 35 1967-2002 98 -19 -54 16

25 1977-2002 119 7 -19 39

10 1992-2002 230 24 5 54

5 1997-2002 300 8 -3 30

CBC/BBS England 35 1967-2002 69 -26 -65 9

25 1977-2002 80 -4 -32 20

10 1992-2002 149 17 -3 40

5 1997-2002 189 7 -5 24

WBS waterways 27 1975-2002 43 -14 -42 33

25 1977-2002 44 -23 -45 11

10 1992-2002 54 0 -16 22

5 1997-2002 51 -3 -16 13

CES adults 18 1984-2002 63 -18 . .

10 1992-2002 77 -25 . . [>25*]

5 1997-2002 77 -22 . .

CES juveniles 18 1984-2002 60 -45 . . [>25]

10 1992-2002 73 -46 . . [>25*]

5 1997-2002 74 -32 . . [>25*]

BBS UK 9 1994-2003 241 -9 -21 4

BBS England 9 1994-2003 152 -6 -20 11

BBS Scotland 9 1994-2003 47 -6 -33 32

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	34	1968-2002	39	Curvilinear	4.95 eggs	4.88 eggs	-0.07 eggs
Brood size	34	1968-2002	61	None
Daily failure rate (eggs)	34	1968-2002	46	Linear decline	0.013 nests/day	0.0066 nests/day	-0.0064 nests/day
Daily failure rate (chicks)	34	1968-2002	52	None
Laying date	34	1968-2002	52	None
Percentage juveniles (CES)	18	1984-2002	68	Smoothed trend	176 productivity index	102 productivity index	-43%[>25]
Percentage juveniles (CES)	10	1992-2002	83	Smoothed trend	150 productivity index	102 productivity index	*-33%[>25]**
Percentage juveniles (CES)	5	1997-2002	84	Smoothed trend	119 productivity index	102 productivity index	-16%

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: Baillie, S.R., Marchant, J.H., Crick, H.Q.P., Noble, D.G., 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. (2005) Breeding Birds in the Wider Countryside: their conservation status 2004. BTO Research Report No. 385. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Susan Waghorn and Iain Downie: Last updated 18 January, 2006