Temporal and spatial correlation in chick production of willow grouse Lagopus lagopus in Sweden and Norway

Abstract We analysed the spatial and temporal dynamics of chick production of willow grouse Lagopus lagopus in the Swedish and Norwegian mountain region using harvest data covering 24–38 years and line-transect counts covering 6–10 years from the period 1960–2003. Juvenile and adult grouse were counted in the bag of harvested willow grouse in late August and throughout September at six sites in Sweden and Norway. In addition, numbers of juvenile and adult willow grouse were obtained from line-transect counts at 21 sites in Sweden just before the hunting season started on 25 August. The juvenile:adult ratio from the harvest data, estimated as number of juveniles per two adults, showed similar long-term averages and distributions between all six sites. The results from the line-transect counts revealed an overall higher average and a greater range of production between sites. We suggest that the difference between estimates based on line-transect counts and harvest data are caused by hunter behaviour. Hunte...