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BLACKBIRD Turdus merula
 
Conservation Listings Long term trend

Table 4/Amber
(25-49% Population decline)

Biodiversity Steering Group: Unlisted

UK: Moderate decline
 
Status Summary
Both the CBC and the CES show long-term declines in Blackbird abundance; the CBC shows that this decline began in the mid-1970s. 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 its occurrence 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 30 1968-1998 225 -26 -34 -19 >25  
  25 1973-1998 231 -25 -32 -18 >25  
  10 1988-1998 215 -6 -10 0    
  5 1993-1998 223 1 -2 5    
CBC farmland 30 1968-1998 97 -42 -47 -34 >25  
  25 1973-1998 96 -38 -44 -32 >25  
  10 1988-1998 95 -13 -18 -7    
  5 1993-1998 96 -4 -9 1    
CBC woodland 30 1968-1998 85 -12 . .    
  25 1973-1998 91 -11 . .    
  10 1988-1998 96 1 . .    
  5 1993-1998 102 5 . .    
CES adults 14 1984-1998 93 -19 . .    
  10 1988-1998 106 -22 . .    
  5 1993-1998 115 -8 . .    
CES juveniles 14 1984-1998 83 -30 . . [>25]  
  10 1988-1998 95 -1 . .    
  5 1993-1998 104 -7 . .    
BBS UK 5 1994-1999 1724 12 9 15    
BBS England 5 1994-1999 1392 13 10 16    
BBS Scotland 5 1994-1999 142 4 -8 17    
BBS Wales 5 1994-1999 129 13 2 26    
BBS N.Ireland 5 1994-1999 51 47 13 91    
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 30 1968-1998 94 None        
Brood size 30 1968-1998 115 None        
Daily failure rate (eggs) 30 1968-1998 132 None        
Daily failure rate (chicks) 30 1968-1998 111 None        
Laying date 30 1968-1998 113 None        
Percentage juveniles (CES) 14 1984-1998 95 Smoothed trend 108 productivity index 100 productivity index -8%  
Percentage juveniles (CES) 10 1988-1998 108 Smoothed trend 79 productivity index 100 productivity index 26%  
Percentage juveniles (CES) 5 1993-1998 116 Smoothed trend 96 productivity index 100 productivity index 4%  
 
   


The report should be cited as: Baillie, S.R., Crick, H.Q.P., Balmer, D.E., Bashford, R.I., Beaven, L.P., Freeman, S.N., Marchant, J.H., Noble, D.G., Raven, M.J., Siriwardena, G.M., Thewlis, R. and Wernham, C.V. (2001) Breeding Birds in the Wider Countryside: their conservation status 2000. BTO Research Report No. 252. BTO, Thetford. (http://www.bto.org/birdtrends)




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