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

2.12.4 Competitive behaviour
No information pertinent to connectivity, was found.
2.12.5 Habitat use
No information pertinent to connectivity, was found.
2.12.6 Winter behaviour
No information pertinent to connectivity, was found.
2.12.7 Dispersal
Female dispersal distances
Within the UK, black grouse are essentially sedentary (Toms, 2002). Dispersal is
primarily confined to first-year hens, with adults of both sexes and first-year cocks
showing high site fidelity (Warren & Baines, 2002; Caizergues & Ellison, 2002).
The majority of hens disperse in their first winter to settle amongst other lekking
groups. Radio-tracking studies, in the French Alps (Caizergues & Ellison, 2002) and
in the north Pennines (Warren & Baines, 2002) show a marked gender contrast in
post-fledging dispersal. In the former study, 81% of the females left the 840ha
survey area to nest 5-29km from their site of capture. In the latter study none of the
eight first-year hens remained within the study site, with distance travelled ranging
between 4.5km and 19.0km (mean: 9.3km) from their natal area (Calladine, 2002).
As genetic studies in Finland confirm the high level of male philopatry to their natal
areas, the conclusion is that the long-term survival of leks relies on immigration of
hens from surrounding areas.
This suggests that a development which inhibits dispersal may contribute to lek
isolation. This is particularly true where leks are further apart. This loss of
connectivity was associated with reduced males in attendance and declining
populations in one study of conifer plantations in Argyll (Haysom, 2001).
In order to avoid such isolation and declines, Caizergues & Ellison (2002) suggest
the mean dispersal distance (4km in the Alps) should be used to ensure connectivity
between lekking groups is maintained. In the North Pennines, the mean natal
dispersal distance was 9km (Warren & Baines, 2002), suggesting a slightly more
dispersed lek pattern is sustainable.
Potential physical barriers to dispersal in the UK possibly include some of the higher
mountains and water, the latter especially for island or peninsular populations
(Calladine, 2002).
2.12.8 Male dispersal distances
Males attend established leks through the year, except when moulting. Home ranges
of males attending these leks overlap considerably (Cayford & Hope Jones, 1989)
and are discreet from males attending adjacent leks.
Where leks are established, the majority of cocks remain close to their natal sites.
The survivors ultimately recruit into these sites. In the north Pennines study by
Warren & Baines (2002), all 11 of the first-year cocks remained within 1km of their
natal site. Interestingly, however, small numbers of males have been recorded
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