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

1986). A pair on a home range in the western Highlands, which has up to 12
recorded eyries within 3kms of each other, has been recorded moving 1.25km in
consecutive years to alternative nest sites (Enda McLoughlin, unpublished data). A
pair in the Cairngorms, which has been recorded using four different eyries, has been
recorded moving to alternative nest sites between 1.5km and 2.5km apart in
consecutive years (Dave Lambie pers. comm.). On Skye, alternative nest sites tend
to be no more than 2km apart in consecutive years (Ken Crane pers. comm.). In
areas such as West Sutherland, alternative nest sites may be further apart (up to
6km) due to low prey density (Colin Crooke pers. comm.).
2.6.3 Display flights
Display flights are a function of territoriality which increases in frequency from
autumn and peaks at the end of the pre-laying period in early spring (Watson, 1997).
The purpose of display flights are a form of passive aggression towards neighbouring
breeders and intruding non-breeders, the latter especially in early winter.
During a long-term study of golden eagles on Skye, males were recorded displaying
throughout their territory, with display flights on the same territory occurring up to
6km apart (Ken Crane pers. comm.). Collopy & Edwards (1985, in Watson, 1997)
recorded golden eagles in Idaho displaying near boundaries, within view of other
territorial golden eagles, and displaying simultaneously with neighbouring territorial
pairs.
Most displays fall roughly into three simple patterns (Crane & Nellist, 1999):
1) ‘on the spot’: forward display into a strong head wind, with the forward
motion being counteracted by the reversing force of the wind;
2) ‘travelling’: forward undulating display flight continued over a relatively
straight large distance; and
3) ‘in a circle’: undulating display flight undertaken in a large circle.
2.6.4 Competitive behaviour
Edge of territory interactions with conspecifics
Territory boundaries are marked, as explained above, by display. A winter study by
Crane & Nellist (1999) found display activity by a young resident pair attempting to
expand their territory was double that of the combined displays of two older,
neighbouring pairs. These two well established pairs had little or no aggressive
interactions and their borders seemed undisputed. Aggression towards neighbouring
resident breeders is generally rare (but can exist in high density populations), whilst
aggression towards non-breeders is common (Haller, 1982 and Bergo, 1987a, both
in Watson, 1997; Crane & Nellist, 1999). Intrusions into occupied territories are rare,
and birds will generally stop at the boundary of their territory, but intrusions do
occasionally occur (Ken Crane pers. comm.). However, intrusions into currently
unoccupied territories are more frequent (Ken Crane pers. comm.).
These interactions usually involve chases and dives in which the intruder defends
itself by rolling over and presenting its talons, sometimes going through a 360° roll
(Crane & Nellist, 1999).
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