The British Trust for Ornithology
BLACKBIRD
Turdus merula
Blackbird © Tommy Holden
 
Conservation listings

Table 4/Amber (25-49% Population decline)
Biodiversity Steering Group: Unlisted

  Long-term trend
UK: Shallow/moderate decline
 
Status summary
Both the CBC and the CES show long-term declines in Blackbird abundance. CBC data indicate that this decline began in the mid-1970s although recent CBC and BBS data both suggest that the population may be starting to recover. Productivity shows no clear temporal trend and it is likely that changes in survival have driven the decline (Siriwardena et al. 1998a). Agricultural intensification is likely to have contributed to the decline (Fuller et al. 1995), but the fact that numbers have fallen in woodland as well as farmland suggests that additional causes may exist. Recent increases apparent in the CBC and BBS index series suggest that the decline may have ceased.
 
 
Table of population changes for Blackbird
Source Period
(yrs)
Years Plots
(n)
Change
(%)
Lower
limit
Upper
limit
Alert Comment
CBC all habitats 31 1968-1999 225 -25 -30 -17    
  25 1974-1999 232 -22 -28 -15    
  10 1989-1999 216 -1 -5 4    
  5 1994-1999 221 7 4 10    
CBC farmland 31 1968-1999 97 -38 -46 -30 >25  
  25 1974-1999 96 -34 -41 -27 >25  
  10 1989-1999 96 -7 -13 -1    
  5 1994-1999 96 5 -1 9    
CBC woodland 31 1968-1999 85 -9 -22 5    
  25 1974-1999 92 -8 -18 6    
  10 1989-1999 97 5 -3 15    
  5 1994-1999 101 9 3 15    
CES adults 15 1984-1999 95 -18 . .    
  10 1989-1999 110 -18 . .    
  5 1994-1999 117 -5 . .    
CES juveniles 15 1984-1999 85 -24 . .    
  10 1989-1999 99 4 . .    
  5 1994-1999 105 -5 . .    
BBS UK 6 1994-2000 1787 13 10 16    
BBS England 6 1994-2000 1438 10 7 13    
BBS Scotland 6 1994-2000 144 2 -10 15    
BBS Wales 6 1994-2000 141 19 8 32    
BBS N.Ireland 6 1994-2000 55 125 76 188    
The Breeding Bird Survey is jointly funded by BTO, JNCC and RSPB
 
 
Table of productivity information for Blackbird
Variable Period
(yrs)
Years Mean
annual
sample
Trend Predicted
in first year
Predicted
in last year
Change Comment
Clutch size 31 1968-1999 95 None        
Brood size 31 1968-1999 119 None        
Daily failure rate (eggs) 31 1968-1999 136 None        
Daily failure rate (chicks) 31 1968-1999 115 Linear decline 0.0289 nests/day 0.0223 nests/day -0.0066 nests/day  
Laying date 31 1968-1999 116 None        
Percentage juveniles (CES) 15 1984-1999 97 Smoothed trend 104 productivity index 100 productivity index -4%  
Percentage juveniles (CES) 10 1989-1999 113 Smoothed trend 81 productivity index 100 productivity index 24%  
Percentage juveniles (CES) 5 1994-1999 119 Smoothed trend 96 productivity index 100 productivity index 4%  
 




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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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