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BTO Blueline
HEN HARRIER
Circus cyaneus

Hen Harrier © John Marchant
 
Conservation listings
Europe: SPEC category 3 (depleted)
UK: red (historical decline)
Long-term trend
UK: stable (between 1988-89 and 1998)
Distribution maps
Distribution maps for this species are not currently available online (see Atlases species help)
Status summary
Red-listed because of substantial declines over the last two centuries, this species has suffered from persecution on grouse moors (Etheridge et al. 1997) and recently also from loss of habitat as forestry plantations have matured (Bibby & Etheridge 1993). The UK population was unchanged between surveys in 1988-89 and 1998, although there were declines in Orkney and England and increases in Northern Ireland and the Isle of Man (DETR 2000). Although average clutch size has declined substantially since the mid 1980s, further investigation has shown that this trend is due to increased proportions in recent years of records from Orkney, where clutch sizes tend to be smaller than in mainland Britain (Summers 1998, Crick 1998).
Annual breeding population changes for this species
are not currently monitored by BTO
Table of productivity information for Hen Harrier
Variable Period
(yrs)		 Years Mean
annual
sample		 Trend Predicted
in first year		 Predicted
in last year		 Change Comment
Clutch size 34 1968-2002 12 Curvilinear 5.56 eggs 4.73 eggs -0.83 eggs Small sample
Brood size 34 1968-2002 19 None       Small sample
Daily failure rate (eggs) 34 1968-2002 11 None       Small sample
Daily failure rate (chicks) 34 1968-2002 13 None       Small sample
Clutch size graph
Brood size graph
Egg nest failure graph
Chick nest failure graph

 

Insufficient data on laying date
available for this species

 

 

Insufficient data on CES
available for this species

 
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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