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2.4 Hen harrier 2.4.1 Foraging Foraging range The foraging range of hen harrier is poorly understood due to a lack of quantitative data (Bright et al., 2006). Estimates for Scottish birds are 3-4km for males and 2- 3km for females, with males consistently ranging further than females (Watson, 1977). Based on data from Angus/Aberdeenshire, Scotland (Picozzi, 1978), it was estimated that foraging ranges can be greater than 1500ha in area, which would be equivalent to a foraging distance of approximately 2.2km. Data on range sizes are available from radio-tracking studies at Langholm, Orkney and Galloway (Arroyo et al., 2005, 2006). Average estimates of the ranging area used 90% of the time for male hen harriers varied between 650 and 1180ha (equivalent to foraging distances of approximately 1.4km and 1.9km), depending on the method of analysis. Equivalent figures for females ranged between 290 and 350ha (equivalent to foraging distances of approximately 1.0km and 1.1km). For each method of analysis, female home ranges were almost half of those of males. In shape, female home ranges were roughly circular around the nest sites, whereas those of males were not necessarily so, and a preferred foraging direction was apparent in at least three of the monitored males (though there is no information on the factors determining this direction). In terms of distances travelled from the nest by radio-tagged birds in the above study (Arroyo et al., 2005, 2006), 93% of female fixes were within 2km of the nest and 70% were within 1km of the nest. In contrast, 35% of male fixes were further than 2km from the nest, and the maximum distance from the nest at which a male was recorded was 8.5km. Foraging distances of up to 10km have been recorded in Uist, for males breeding in bog areas and foraging on the coast to prey on migrant and breeding waders (Andrew Stevenson pers. comm.). A female has been recorded in Uist carrying prey approximately 8km from a nest. 2.4.2 Prediction models Madders (2003) provides a model that aims to predict the relative use made of different parts of local ranges occupied by hen harrier during the breeding season. The model proposes to use existing data sources and takes account of nest proximity, vegetation cover and structure, and the distribution of linear habitat features. The model predicts harrier ranging behaviour using a standard index based on nest distance. This avoids the need to make assumptions about an individual’s foraging range or ‘core area’. 2.4.3 Nesting Nest site fidelity In Scotland, hen harriers usually nest in the same area in successive years, with the median distance moved between sites from year to year being 0.71km (Etheridge et al., 1997). The largest movement, which was by a female, was 188km. Picozzi (1984a, b) found that, in Orkney, female harriers that moved into a new territory moved further following breeding failure than after successful breeding. Etheridge et al. (1997) also found a small, but non-significant, difference in distance 8
moved in successive years between successful female breeders (0.63km) and unsuccessful females (0.81km). 2.4.4 Display flights The first tentative display flights begin in late March, with full displays by late April (Watson, 1977). Male displays generally ceases about the time the eggs are laid, whilst females display late into the fledging period. The male’s ‘sky-dancing’ display consists of a steep climb of approximately 30m, followed by a roll and dive (Cramp & Simmons, 1980). The performance is generally at heights between 30 and 150m, and may be repeated several times; 105 successive dives have been recorded during a single display. Display flights can also involve high circling, at up to 500m from the ground (Cramp & Simmons, 1980). Males will display over several possible nesting stations, travelling from hill to hill and rising above each in turn. Females often also display, although their flights take a ‘switch-backing’ course rather than the steep ascents and descents of the male. Female displays, therefore, tend to take place at lower heights than those of males. The majority of display flights are expected to be around the nest site (Hardey et al., 2006). Males displaying near the Strathy Forest have been recorded as displaying up to 1km from the nest site (RPS data). 2.4.5 Competitive behaviour Edge of territory interactions with conspecifics Male hen harriers actively defend a nest territory of approximately 600m in diameter (Watson, 1977). Foraging ranges of males overlap extensively, whilst ranges of females do so to a lesser extent (Arroyo et al., 2005, 2006). Hen harrier intra-specific aggression peaks early in the season, is mainly intra-sexual, and increases with the number of neighbours (Garcia & Arroyo, 2002). 2.4.6 Habitat use Likely habitat use In Scotland, the majority of pairs nest in heather moorland, with ling heather (Calluna vulgaris) typically being dominant in the immediate vicinity. Species such as bracken (Pteridium aquilinum), bog myrtle (Myrica gale), rushes (Juncus spp.), willow (Salix spp.) and purple moor grass (Molinia caerulea) may also be present along with open and closed forestry plantation (Potts, 1998; Hardey et al., 2006). The importance of heather in Scottish populations has been demonstrated by Redpath et al. (1998). They found that 94% of hen harrier nests were located in rank, but not degenerate heather, with an average height of 46cm. They also found that the nests tended to be nearer streams than would be expected by chance, and that there was an indication of preference for north-west facing slopes. Hen harriers prefer foraging in young first rotation coniferous forests and select heathland and heterogeneous grassland habitats over closed canopy woodland (Madders, 2000). Foraging hen harriers tend to avoid afforested habitats with lots of foliage greater than 5m tall, homogeneous grassland areas, and areas with a large cover of bracken (Madders, 2000). 9
Page 1 and 2: Scottish Natural Heritage Commissio
Page 3 and 4: COMMISSIONED REPORT Summary Literat
Page 5 and 6: Tables Page Table 1 - Species revie
Page 7 and 8: 1. INTRODUCTION Proposals for opera
Page 9 and 10: 2. SPECIES ACCOUNTS 2.1 Red-throate
Page 11 and 12: 2.2 Black-throated diver 2.2.1 Fora
Page 13: High flying, up to 1000m, can also
Page 17 and 18: 2.5 Goshawk 2.5.1 Foraging Core for
Page 19 and 20: Nest locations were regularly distr
Page 21 and 22: Ringing recoveries of an adult fema
Page 23 and 24: 1986). A pair on a home range in th
Page 25 and 26: Grant & McGrady (1999) followed two
Page 27 and 28: 2.7.5 Habitat use Likely habitat us
Page 33 and 34: will subsequently role away, or til
Page 35 and 36: 2.11 Short-eared Owl 2.11.1 Foragin
Page 37 and 38: 2.12 Black grouse 2.12.1 Foraging H
Page 39 and 40: making longer movements (5 to 10km)
Page 41 and 42: Thompson, 1998). Other interactions
Page 43 and 44: 2.14 Greenshank 2.14.1 Foraging Cor
Page 45 and 46: 2.15 Dunlin 2.15.1 Foraging Foragin
Page 47 and 48: 2.16 Curlew 2.16.1 Foraging Core fo
Page 49 and 50: 2.18 Wintering geese 2.18.1 Foragin
Page 51 and 52: to about 7 km from the roost (Malco
Page 53 and 54: 3.2 Foraging ranges during winter s
Page 55 and 56: 4. REFERENCES Arroyo, B.E. Leckie,
Page 57 and 58: Fuller, R.J. & Lloyd, D. (1981). Th
Page 59 and 60: Mearns, R. (1985). The hunting rang
Page 61 and 62: Rebecca, G.W. & Bainbridge, I.P. (1
Page 63 and 64: Whittingham, M.J., Percival, S.M. &

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