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

2.10 White-tailed eagle
2.10.1 Foraging
Foraging range
Territory ranges are highly variable between populations and are dependent upon
suitable breeding habitat and prey availability. In coastal areas of Norway where
prey is readily available, territories are constricted, with only a small area directly
around the nesting site being defended. In this situation foraging areas are used by
more than one pair (Bright et al., 2006). In favourable habitats in mainland Europe,
neighbouring pairs may nest as close as 1-2km apart (Cramp & Simmons, 1980). On
Mull, with the highest average population density in Scotland, the mean distance
between neighbouring pairs nest is 8.6km (range: 3.2-14km; Hardey et al., 2006).
A study of a population of white-tailed eagles in Russia recorded birds hunting a
mean area of 1310ha (Masterov, 2003 in Bright et al., 2006). It was observed that
most foraging activity took place within 5km of the nest site but some pairs flew up to
13km from the nest to forage.
A study of a white-tailed eagle population in Schleswig-Holstein, Germany found that
the 16 breeding pairs in 1995 had a mean territory size of 6200ha (Struwe-Juhl,
1996a & b). This is equivalent to a mean foraging distance of 4.4km per pair.
2.10.2 Nesting
Nest site fidelity
Pairs tend to be fairly site faithful, and adults are resident in their territory throughout
the majority of their range (Halley, 1998). Throughout their range there is evidence
suggesting some individual territories have been occupied for many years. For
example, one territory on Mull has been occupied since 1986. Studies in Finland and
Sweden have shown that some territories have been in use for several decades, or
even centuries, and in Iceland one territory has been consistently occupied for the
last 150 years (Bright et al., 2006).
White-tailed eagles may have between one and 11 nest sites within their nesting
range, generally ranging from 2m to 3km apart (mean: 480m; Cramp & Simmons,
1980). On Rum, six out of 10 pairs studied had one or two alternative eyries, with the
distance between alternate nesting sites often being within 2km (Love, 1988). On
Mull, alternative nest sites have been recorded several kilometres apart, whilst on
Skye they have been found up to 12km apart (Bright et al., 2006). Larger distances
between alternative nest sites tend to be more prevalent amongst inexperienced
birds (Hardey et al., 2006). Studies of a population of white-tailed eagles in Lithuania
have found that pairs tend to nest within 1.3km from the previous year’s nest (Jusys
& Mecionis, 1992).
2.10.3 Display flights
Display flights generally occur in the nesting territory and immediate vicinity, as early
as early/mid December in long-standing resident pairs. The display flights involve
either one or both birds of the pair circling high over the nesting area. Mutual circling
can occur as far as 3km from the eyrie, but is generally only over a limited area, at
heights below 200m (Cramp & Simmons, 1980).
During mutual circling, more elaborate displays can ensue (Cramp & Simmons,
1980). This can involve the pair flying between 1 and 6m apart and moving in
concentric circles. The upper bird will either pounce towards the lower bird, which
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