An epizootic of sarcoptic mange among red foxes Vulpes vulpes reached central Norway in 1976, and by 1986 it had spread to the whole country, resulting in a severe decline in the red fox population. We analyse the change in the hunting bags of the predator species red fox and pine marten Martes martes, and the prey species capercaillie Tetrao urogallus, black grouse Tetrao tetrix, mountain hare Lepus timidus and willow grouse Lagopus I. lagopus from the period prior to and during the mange epizootic. The data are gathered from publications by Statistics Norway and are based on answers from more than 5,000 hunters yearly. On the national level, the hunting bags of capercaillie, black grouse, mountain hare and pine marten were significantly negatively correlated with that of the red fox. When the time series at the national level were detrended, there were positive correlations between the hunting bags of all species without time lag, except that of pine marten, which lagged one year behind the other species. At the local level there were negative correlations between the hunting bag of red fox and those of the small game species except for willow grouse. The study confirms that the red fox is a keystone predator in Scandinavia.

Communal roosting in birds may function to enhance foraging e¤ciency, as explained by the information centre hypothesis, which predicts that successful foragers return from the roost to the rewarding food patch and that birds ignorant of this food follow knowledgeable roost-mates. We tested these predictions by exposing 34 radio-tagged, free-ranging, £ock-living hooded crows (Corvus corone cornix) to a novel experimental set-up mimicking a super£uous food patch with maximum temporal and spatial unpredictability. Each replicate lasted two days and was located on a new site. Data were collected during ten replicates over three years. First, a crow was more likely to visit the experimental food patch on the second day when it had been there on the ¢rst day. Second, when a crow had not been at this food patch on the ¢rst day, it was more likely to visit it on the second day if it had roosted together with a crow that had been there on the ¢rst day, but only if this knowledgeable roost-mate returned to the food patch on the second day. Our results support the information centre hypothesis and suggest that communal roosting might function to enhance foraging e¤ciency in hooded crows.

No abstract

Gatherings of birds at preroosts before departure to nocturnal roosts have rarely been studied and their function is poorly understood. We recorded preroosting behaviour of hooded crows, Corvus corone cornix, in a mixed farmland-forest landscape in southeastern Norway during fall and winter, by selecting gatherings attended by at least one radio-tagged crow for observation. The preroosting crows perched in a highly aggregated and exposed group and did not forage. As the amount of snowfall during the preceding 24 h increased, an indication of sudden difficulty in finding food, the maximum number of crows that gathered increased, the duration of the gathering increased, and the straight-line distance covered by the radio-tagged crows from preroost to roost increased. The crows flew conspicuously in formation more often and for a longer time when on their way from preroost to roost on days with stronger winds. The results suggest that, in hooded crows, a preroost gathering is not simply a consequence of many individuals approaching the same roosting area but has some function, presumably that of maximizing the probability of finding rewarding food sites the next day by finding is a communal roost where information on the location of these sites may be obtained.

No abstract