Smith, A.A. 1997: Dispersal and movements in a Swedish willow grouse Lagopus lagopus population. - Wildl. Biol. 3: 279.
Between 1992 and 1995, radio-telemetry was used to study landscape scale patterns of movement in an upland Swedish population of willow grouse Lagopus lagopus. The net first-year dispersal distances of juvenile females (mean = 11.4 km) differed (Z-test, P > 0.008) from those of juvenile males (mean = 2.6 km). Juvenile females dispersed over a few days in either or both of the periods October-January and April-May. Juvenile male dispersal was broadly continuous throughout the year. Two-thirds of marked juvenile females dispersed > 6 km from their brood site. Differences within sexes were not associated with apparent breeding success, body condition index, or grouse density on the natal area. No age or sex class showed density-dependent immigration being induced by lowering grouse densities on a central hunting area. Adult females were migratory between wintering areas used as a juvenile and their first breeding site; 56% migrated over 3 km. Timing of migration for adults was similar to that of juvenile females. Adult males and short-distance migrant females had similar annual range sizes (4 km²). Yearling females that failed to fledge young tended to disperse to a new breeding range the following year. Adult and juvenile female movements during spring were similar in all respects. Return in spring to breeding sites appeared dependent on snow cover at higher altitudes. Excursions lasting 1-5 days from winter to breeding areas were observed during spring for some females. Variable dispersal distances have important implications depending on scale effects. At scales of 5 km, movements of juveniles and adult females have a role in redistributing birds within landscape units. At landscape scales, only dispersing juvenile females and a few adult females are important in inter-population contacts.
Key words: Lagopus lagopus, landscape, migration, movements, natal dispersal, Sweden, willow grouse,
A. Adam Smith, Edward Grey Institute, University of Oxford, Department of Zoology, South Parks Road, Oxford, OX1 3PS, United Kingdom