Literature review to assess bird species connectivity to Special ...

2.5 Goshawk
2.5.1 Foraging
Core foraging range
Adult goshawks are sedentary in Britain and Ireland (Petty, 2002, 2007b). The size
of goshawk home-ranges, and nest density, vary considerably with the availability of
suitable prey (Petty, 2007a) and woodland (Kenward, 1982, 2006; Hardey et al.,
2006; Petty, 2007b). Woodland edge is a very important resource for this ambush
predator; individual goshawks with the greatest access to woodland edge
consequently have the smallest home ranges (Kenward, 1982).
Goshawks defend only the nesting territory against other goshawks (Cramp &
Simmons, 1980), and hunt within large overlapping home ranges (Kenward, 2006;
Hardey et al., 2006). In suitable woodland habitat in the UK and abroad, nest sites
are regularly spaced (UK: Petty, 1989; Arizona, United States: Reich et al,. 2004).
Nearest neighbour distances for nest locations in woodland blocks in lowland Britain
vary between 1.0km and 3.7km (Hardey et al., 2006).
Radio-tagged goshawks studied during autumn in Sweden (Kenward, 1977) had
widely overlapping home ranges. From 14 ranges defined, the two smallest (both
about 700ha; equivalent to a foraging distance of approximately 1.5km) belonged to
adults, and the two largest (4600 and 4900ha; equivalent to foraging distances of
approximately 3.8km and 3.9km, respectively) belonged to juveniles. However, the
ranges of juveniles were large partly because these birds occasionally flew up to
10km outside their regular areas. Such flights involved soaring, and may have
served for exploration.
Goshawk show wide variability in ‘area per territory’. In the UK these vary between
620 (Marquiss et al., 2003) and 2500ha (Petty, 2006 in Petty, 2007b), with a similar
pattern across Europe. The situation is also similar in North America, but ‘areas per
territory’ of up to 9000ha have been recorded (Wagenknecht et al., 1998). Since
birds tend to hunt within overlapping home ranges, these areas cannot be used to
estimate foraging distances. Based on observations of breeding goshawk in
Scotland, however, most hunting is believed to take place within 10km of the nest
site (David Anderson pers. comm.).
2.5.2 Buffers around the nest site
Goshawk adults use an area 100-200m from the nest site intensively for perching,
plucking and feeding (Kenward, 2006). Petty (1998) prescribes 400m, or an area of
50ha, as an appropriate buffer around goshawk nest sites to prevent disturbance.
This is based on goshawk territories from north-east Scotland and the Scottish
Borders. The site-specific characteristics of the nest area, and surrounding
woodland size and structure, should be used to determine the exact extent of the
buffer required around an active nest site.
Desimone & Hays (2004) propose a method for the management of the breeding
home range of the Northern goshawk, including nest areas, nest area clusters, postfledging
areas and a foraging area. The 2442ha total home range includes the
foraging area (2200ha), the post-fledging area (170ha) and nest areas (72ha). This
method of management for the goshawk home range (during the breeding season)
would use a buffer radius of 2.79km.
Penteriani & Faivre (2001) found no significant difference in the productivity of
goshawk pairs reproducing in unlogged vs. logged stands. They observed that
87.5% of goshawk pairs nesting in logged stands moved away only when the original
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