The British Trust for Ornithology
HEN HARRIER
Circus cyaneus

Conservation Listings

Table 2/Red (Historical decline)
Biodiversity Steering Group Conservation Concern List
Long term trend
UK: Stable since 1988-89  
Status Summary
Listed because of substantial declines over the last 200 years, this species has suffered from persecution on grouse moors (Etheridge et al. 1997) and more recently 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 but increases in Northern Ireland and 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 of records from Orkney in recent years, where clutch sizes tend to be smaller than on the mainland (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 31 1968-1999 13 Linear decline 5.05 eggs 4.45 eggs -0.6 eggs Small sample
Brood size 31 1968-1999 19 None       Small sample
Daily failure rate (eggs) 31 1968-1999 11 None       Small sample
Daily failure rate (chicks) 31 1968-1999 13 None       Small sample

 

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., 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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