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BTO Blueline
GARDEN WARBLER
Sylvia borin
 Garden 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, England: shallow decline
UK population size
190,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)
Status summary
Garden Warbler abundance has varied alongside that of other trans-Saharan migrant warblers (Siriwardena et al. 1998b), probably reflecting the influence of changes in their winter environment. Despite large short-term fluctuations in abundance, the CBC/BBS and CES now both suggest the population is in long-term decline. There has been a substantial increase in nest losses at the chick stage, and post-fledging productivity, as measured by the CES, has declined sharply since 1983, raising BTO alerts.
 

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

Source Period
(yrs)		 Years Plots
(n)		 Change
(%)		 Lower
limit		 Upper
limit		 Alert Comment
CBC/BBS England 37 1967-2004 152 -24 -48 23    
  25 1979-2004 195 12 -14 50    
  10 1994-2004 364 -17 -25 -7    
  5 1999-2004 351 -21 -28 -14    
CBC/BBS UK 37 1967-2004 179 -20 -44 27    
  25 1979-2004 232 26 -3 74    
  10 1994-2004 443 -12 -20 -1    
  5 1999-2004 431 -16 -23 -8    
CES adults 20 1984-2004 64 -22 -45 11    
  10 1994-2004 71 -24 -37 -9    
  5 1999-2004 63 -23 -34 -8    
CES juveniles 20 1984-2004 63 -45 -58 -19 >25  
  10 1994-2004 71 -39 -49 -30 >25  
  5 1999-2004 64 -16 -30 2    
BBS UK 11 1994-2005 381 -8 -18 3    
BBS England 11 1994-2005 310 -12 -23 0    
BBS Wales 11 1994-2005 53 -37 -54 -15 (>25)  

BBS acknowledgement
 
CBC/BBS England graph
CES adult abundance graph
CES juvenile abundance graph
BBS UK graph
BBS England graph
BBS Wales graph
 

Productivity trends
Table of productivity changes for Garden Warbler

Variable Period
(yrs)		 Years Mean
annual
sample		 Trend Modelled
in first year		 Modelled
in 2004		 Change Comment
Clutch size 36 1968-2004 16 None       Small sample
Brood size 36 1968-2004 25 None       Small sample
Daily failure rate (eggs) 36 1968-2004 22 None       Small sample
Daily failure rate (chicks) 36 1968-2004 19 Linear increase 0.99% nests/day 2.63% nests/day 165.7% Small sample
Laying date 36 1968-2004 21 Linear decline May 28 May 22 -6 days Small sample
Juvenile to Adult ratio (CES) 20 1984-2004 77 Smoothed trend 147 Index value 104 Index value -32%  
Juvenile to Adult ratio (CES) 10 1994-2004 85 Smoothed trend 102 Index value 104 Index value -2%  
Juvenile to Adult ratio (CES) 5 1999-2004 79 Smoothed trend 77 Index value 104 Index value 30%  

 
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., Barimore, C., Coombes, R.H.,
Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. & Thewlis, R.M. (2007)
Breeding Birds in the Wider Countryside: their conservation status 2006.
BTO Research Report No. 470. BTO, Thetford. (http://www.bto.org/birdtrends)

Pages maintained by Susan Waghorn and Iain Downie: Last updated 4 May, 2007