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

making longer movements (5 to 10km) from their natal area during their first year, but
these are less common (Grant, 2007). The work by Caizergues & Ellison (2002)
revealed only 9% of males had emigrated from the 836ha study area between the
1990 to 1998 research period. In combination, this suggests that a small proportion
of first-year males may disperse more widely.
Leks comprising single birds are more mobile and ephemeral, and may be used for
just one or two years compared to the regular use of traditional leks (Cayford, 1993).
The implications are that in areas with large numbers of single-bird leks (e.g. Cowal,
Argyll), male black grouse movements over greater distances may be more common.
2.12.9 Seasonal movements
The main seasonal movements of black grouse arise from natal dispersal, of which
Caizergues & Ellison (2002) identified two discreet phases; one in autumn (October)
and the other in spring (mid-April to early May). There are periods of reduced
mobility between these phases. The study also showed that mean distance travelled
by females exceeded that of males in autumn but not in spring. These findings tally
with the dispersal patterns identified by Warren & Baines (2002). From a sample of
48 radio-tagged poults they found distinct dispersal periods in late autumn (mean:
10.3km) and again in early spring (mean: 5.8km).
Apart from natal dispersal, both males and females remain in the same general
locality throughout the year and rarely move more than a few kilometres from the lek
they attend in spring (Warren & Baines, 2004).
Winter home ranges of full-grown birds are relatively small and sometimes distinct
from areas used at other times of the year, with birds congregating on particularly
favoured areas (Baines et al., 2002; Calladine, 2002). Examples of favoured winter
habitats are patches of birch and willow, tall vegetation where grazing is restricted,
vestigial areas of ericaceous vegetation, and herb-rich meadows (Willebrand, 1988;
Baines, 1994; Starling-Westerberg, 2001; Baines et al., 2002). In their study, Picozzi
& Catt (1988) identified the greatest use of moorland and rough grassland to be from
the spring to the late summer or early autumn, whilst most use woodland use was
generally during winter.
Ringing data are extremely limited. All 13 recoveries in Scotland have been of
Scottish-ringed birds, with 10 controlled within 9km of the ringing site and three within
10-99km (Grant 2007).
2.12.10 Post-breeding chick dispersal
As reported above, brood home ranges are small and can be under 50ha (Starling,
1990) equivalent to a distance of less than 400m. However, they are more typically
between 10ha and 30ha (Warren & Baines, 2004) equivalent to distances between
180 and 300m. Dispersal by first-year birds is mainly confined to hens, with a mean
autumn dispersal of 10.3km from the natal site to the first breeding location, and early
spring movements of 5.8km (Warren & Baines, 2002).
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