Ptarmigan and grouse species (Lagopus spp.) are thought to be able to compensate for a modest harvest because there is a surplus of breeding birds that are prevented from breeding by territory holders. To estimate the degree of harvest-mortality compensation reliably we experimentally harvested 0%, 15% and 30% of the willow ptarmigan (Lagopus lagopus) on 13 estates ranging from 20 to 54 km2 in size during four hunting seasons in Norway according to a regional block design. Population overwinter growth rate was strongly negatively density dependent, but despite this, and contrary to earlier findings, only 33% of the harvest was compensated for. The lack of compensation was probably caused by long-distance juvenile dispersal that was unaffected by the harvest. The need for large-scale management experiments to detect the effects of harvest was clearly demonstrated: lack of compensation was found only when we used the whole dataset and not when the data were analysed by year or block. Our study shows that it is very difficult to demonstrate a population's lack of harvest compensation and warns against using small-scale, out-of-season or poorly replicated studies as a basis for future harvest-management decisions.

We compared habitat use and diets of young Capercaillie and Black Grouse broods in a boreal forest in southeast Norway. We used pointing dogs to search for broods (N = 83) in mature ''natural'' forest types and examined the crop content of 66 chicks 1-9 weeks old. We also measured the abundance of insects in the habitats where broods were found. Although overlapping substantially in both habitat and diets, there were notable differences: Capercaillie broods were more frequently recorded in bilberry-dominated forest types, whereas Black Grouse preferentially used pine bog forest, a more open habitat with little bilberry. Capercaillie chicks ate proportionally more insects, particularly lepidopteran larvae, and insects dominated their diet for a longer period of time (until age 28-29 days) than in Black Grouse (14-15 days). After reaching their peaks, the quantity of insects in the crops declined rapidly especially in Capercaillie, and in one of 2 years this occurred at a time when insects, including larvae, were still abundant in the habitats. Among plant foods, both species ate large amounts of Bilberry (Vaccinium myrtillus) and Bog Whortleberry (V. uliginosum). The main difference between species was a large proportion of both over-wintered and new, not yet ripe, berries of Cranberry (Oxycoccus quadripetalus) in Black Grouse, and a higher proportion of the forb Melampyrum sylvaticum in Capercaillie. The difference in diets reflected their differential use of habitats; the Vaccinium-preferred habitats of Capercaillie were richer in insects, particularly larvae, than the pine bog habitat preferred by Black Grouse. Because insects, especially larvae, comprised a larger proportion of the diet of Capercaillie chicks and chicks of this species need more food to sustain their rapid growth, Capercaillie is likely to be more sensitive to variation in insect food than Black Grouse. Also, by reducing the abundance of bilberry, the main host plant of larvae chick food, clearcutting forestry has negative effects on the brood habitat quality of both species.

Summary 1.Harvest management requires knowledge of whether the harvest is sustainable as a result of compensatory mechanisms, such as dispersal. The effect of recreational harvesting on dispersal patterns in willow ptarmigan Lagopus lagopus was assessed over four hunting seasons in central Norway. 2.A two-parameter Weibull model was fitted to the observed absolute dispersal distance data using maximum likelihood methods. Estimates of the scale and shape parameters for the dispersal probability distribution were calculated, describing the distribution of observed willow ptarmigan dispersal distances. From the parameter estimates of the dispersal model we estimated the standard deviation of the dispersal displacement relevant for population genetic and spatial population dynamic models. 3. The effect of harvesting on dispersal patterns was examined by testing for differences in the scale and shape parameters of dispersal distance distributions in areas with and without harvest. No effect of harvesting was found, either in adults or juveniles. 4. Breeding dispersal of adult birds was estimated as a dispersal probability distribution with scale parameter a = 402 m and shape parameter b = 2·01, corresponding to a dispersal standard deviation of σ = 284 m. The dispersal probability distribution of adults was not significantly different from a bivariate normal distribution. 5. Natal dispersal had a dispersal probability distribution with scale parameter a = 4206 m and shape parameter b = 1·16, corresponding to a dispersal standard deviation σ = 3728 m. The dispersal probability distribution of juveniles was not significantly different from an exponential distribution. 6. Synthesis and applications . Reduction of the population density of willow ptarmigan through harvesting at moderate densities does not seem to affect the dispersal distances. Thus, if there is little or no difference in the dispersal probability distribution in harvested and non-harvested areas there will be only weak or no compensation for the harvest, given that natural mortality and reproduction is the same in both areas. Thus, erroneously assuming compensation of harvest by immigration into a local population can lead to overharvest.

We used hunting dogs and man to simulate the searching for nests and broods of forest grouse, i.e. capercaillie Tetrao urogallus and black grouse Tetrao tetrix, by mammalian predators. Our aim was to find out if and how forest fragmentation affects the searching efficiency of predators. In total, we found 73 capercaillie and 35 black grouse nests and 20 young capercaillie broods. We calculated that a mammalian predator will detect a capercaillie nest if closer than 1.6 m (95% C.I.: 0.7 ‐ 2.2), a black grouse nest if closer than 1.1 m (95% C.I.: 0.8 ‐ 1.6), and a capercaillie brood if closer than 39 m (95% C.I.: 17 ‐ 89). Nests were distributed in all habitat types, whereas broods were restricted to specific brood habitats. Due to this and the difference in the detection radius between nests and broods, we estimated that the predator gain of searching for broods in brood habitat is about 80 times higher than the gain of searching for nests which are situated in all habitat types in our study area. As young broods concentrate in highly restricted habitats, the predator gain of searching for broods increases exponentially with the loss of brood habitat, whereas it decreases linearly with increasing nest predation. We discuss this mechanism as a possible process explaining the observed decline in capercaillie populations in fragmented forests and consider its implications for grouse management.

In a population study during 1979–1988 at Varaldskogen in southeastern Norway, 234 capercaillie Tetrao urogallus nests and broods were classified as first nests or renests. Of the females that had their first nest depredated, 9–87% (mean 36%) renested. Over a 6‐year period, autumn brood production increased from 30 to 38% due to renesting. Renesting is physically demanding for the females; the eggs in renests are fewer and smaller, and the females take more and longer recesses than when incubating first nests. All the females incubated their first nests till the eggs hatched or the nest was depredated. Two of the renesting females took more and longer recesses until they gave up their nests. The ability to renest seems to be weight‐related, as yearling females, which weigh less than adult females, did not renest, and the weight of adult females on leks was highest in the two years when most renesting occurred. The female will renest if the nest is depredated during the first three days of incubation. Each of the following 19 days, all years combined, a mean of 26% of females who lost their nests renested. Capercaillie renesting was related to the vole cycle; it was highest in the year before the small rodents peaked and decreased through the vole crash and the year after.