BTO - Breeding Birds of the Wider Countryside

SEDGE WARBLER
Acrocephalus schoenobaenus

Conservation listings

Unlisted/Green
Biodiversity Steering Group
Conservation Concern List

Long-term trend

UK: Fluctuating with no long-term trend
Farmland: Moderate decline

Status summary

Prior to the inception of BBS, Sedge Warbler populations were not represented well by any UK monitoring scheme. However, the CBC identified a decline, especially on farmland, that ceased in the mid-1970s. The populations monitored by the CBC and WBS have since remained more-or-less stable, a pattern also seen in the BBS results for the last seven years. The CES provides the biggest sample for Sedge Warbler and it shows large inter-annual fluctuations and a suggestion of a decline through the 1990s. Detailed analysis of BTO datasets has shown that much of the variation in population size is related to 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). No strong trends are apparent in breeding performance, but CES productivity has shown a steady decline since 1983.

Table of population changes for Sedge Warbler

Source Period
(yrs) Years Plots
(n) Change
(%) Lower
limit Upper
limit Alert Comment

CBC all habitats 31 1968-1999 44 -16 -43 7 Unrepresentative

25 1974-1999 44 23 -7 47 Unrepresentative

10 1989-1999 39 8 -10 34 Unrepresentative

5 1994-1999 41 15 1 28 Unrepresentative

CBC farmland 31 1968-1999 24 -44 -69 9 Unrepresentative

25 1974-1999 23 11 -31 95 Unrepresentative

10 1989-1999 23 7 -15 43 Unrepresentative

5 1994-1999 24 16 -5 33 Unrepresentative

WBS waterways 24 1975-1999 44 -14 -40 39

10 1989-1999 54 -14 -24 1

5 1994-1999 57 0 -8 11

CES adults 15 1984-1999 63 2 . .

10 1989-1999 76 -23 . .

5 1994-1999 85 -13 . .

CES juveniles 15 1984-1999 59 -24 . .

10 1989-1999 72 -43 . . [>25*]

5 1994-1999 80 -24 . .

BBS UK 6 1994-2000 241 55 37 76

BBS England 6 1994-2000 152 30 11 52

BBS Scotland 6 1994-2000 48 86 37 153 Small sample

BBS N.Ireland 6 1994-2000 21 36 -8 102 Small sample

The Breeding Bird Survey is jointly funded by BTO, JNCC and RSPB

Table of productivity information

Variable Period
(yrs) Years Mean
annual
sample Trend Predicted
in first year Predicted
in last year Change Comment

Clutch size 31 1968-1999 41 None

Brood size 31 1968-1999 64 None

Daily failure rate (eggs) 31 1968-1999 48 Linear decline 0.0132 nests/day 0.0073 nests/day -0.0059 nests/day

Daily failure rate (chicks) 31 1968-1999 55 None

Laying date 31 1968-1999 55 None

Percentage juveniles (CES) 15 1984-1999 68 Smoothed trend 157 productivity index 100 productivity index -36%[>25]

Percentage juveniles (CES) 10 1989-1999 81 Smoothed trend 144 productivity index 100 productivity index -31%[>25*]

Percentage juveniles (CES) 5 1994-1999 90 Smoothed trend 129 productivity index 100 productivity index -22%

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This report should be cited as:
Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Beaven, L.P., Downie, I.S., Freeman, S.N., Leech, D.I., Marchant, J.H.,
Noble, D.G., Raven, M.J., Simpkin, A.P., Thewlis, R.M. and Wernham, C.V. (2002) Breeding Birds in the Wider
Countryside: their conservation status 2001. BTO Research Report No. 278. BTO, Thetford. (http://www.bto.org/birdtrends)

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