More than 60,000 km? of the state-owned Swedish mountain range was opened to the public for small game hunting in 1993, and different management strategies were discussed to avoid risk of overharvesting willow ptarmigan Lagopus lagopus. In 1994, the average end of season harvest rate was estimated at less than 10% of the autumn population. However, local variation in harvest rates was high. For example, harvest estimates on a study area with good road access were closer to 30%. The results of several Scandinavian willow ptarmigan studies show average production of 2.8 young per pair. Although the annual variation can be between 0.5 and 6 young per pair, there is no evidence of density dependency. There are only a few estimates of annual survival; mark-recapture methods suggest annual survival of the whole population is about 40%. A population model was developed in which only survival was density dependent. This model was used to investigate the outcome of harvesting a willow ptarmigan population at different rates where natural survival showed either a high, medium, or low response to reduced densities. The model predictions are being compared with earlier published results and preliminary findings of a recent project on willow ptarmigan population dynamics using radio-marked individuals. Comparisons suggest that density-dependent survival and compensatory mortality were weak at the management scale (10-100 km?), and that a better understanding of the mechanisms of movement and dispersal on a landscape level is necessary.

Key words: density dependency, harvest, Lagopus lagopus, modelling, population, Sweden, willow ptarmigan

Tomas Willebrand, Department of Animal Ecology, Swedish University of Agricultural Sciences, 901 83 Ume?, Sweden