Status of the Hen HarrierCircus cyaneusin the UK and the Isle of Man in 1998

The status of the Hen Harrier,Circus cyaneus, in the UK and Isle of Man in 2010

“…The inclusion of single birds produced a larger estimate of 842 pairs (95% CI: 748-969). The number of territorial pairs was significantly lower (P < 0.05) than in 2004, declining by 18% from 806 pairs (Sim et al 2007), and was not significantly different to the numbers of territorial pairs in 1998 (Sim et al 2001 As in previous surveys, the West Highlands held the largest proportion of the Scottish population (36%; (Table 5). However, there were significant declines in the number of Hen Harriers recorded in both mature and young plantation, having decreased by 55% (randomization test, P-value = 0.004) and 74%, respectively, since 2004 (P-value = 0.01).…”

“…However, there were significant declines in the number of Hen Harriers recorded in both mature and young plantation, having decreased by 55% (randomization test, P-value = 0.004) and 74%, respectively, since 2004 (P-value = 0.01). The pattern of habitat use in Scotland in 2010 now resembles that recorded in 1998 when the majority of records (84%) were from heather moor, with none in mature plantation or scrub (Sim et al 2001). In England (100%), Wales (92%), Orkney (99%) and the Isle of Man (57%), all or the majority of territorial pairs and singles were found on heather moorland (Table 5) In Northern Ireland, the majority of the records were from young plantation, a substantial increase from eight pairs (less than 10%) in 2004 to 43 pairs (56%) in 2010.…”

“…Prior to 2004, the population had undergone a substantial increase since the second national survey in 1998, and the estimate in 2010 is still above that from 1998 (570 pairs, 95% CI: 499-640 (Sim et al 2001 The sum of the regional totals differs slightly from the estimated national total due to the differing sampling intensities and small sample sizes in different regions. (Haworth & Fielding 2009), significant declines were recorded in the number of Hen Harriers breeding within forest plantations (young and mature) in Scotland.…”

“…The 2010 Hen Harrier survey follows very closely the design of previous surveys in 1998 and 2004 (Bibby & Etheridge 1993, Sim et al 2001, 2007. The species' range in the UK and the Isle of Man was defined as all 10-km national grid squares with records of Hen Harriers in the breeding season (April to July) since 1968, using the Breeding Bird Atlases from 1968 to 1972 (Sharrock 1976) and from 1988 to 1991 (Gibbons et al 1993).…”

“…Sim et al 2001Sim et al , 2007. In Orkney, the count unit was the number of breeding females due to the extent of polygyny in that population (Balfour & Cadbury 1979, Picozzi 1984.…”