Declines in populations of capercaillie (Tetrao urogallus) and black grouse (Lyrurus tetrix) have been reported from both Central Europe and the continuous boreal forests of Fennoscandia. While intensified land-use is assumed to be the underlying cause of these declines, the mechanisms are not yet understood. Predation is the proximate cause of mortality of eggs, chicks and adults throughout capercaillie and black grouse ranges, but the link between predation and habitat and/or climate change remains unclear. To investigate temporal trends in reproductive output of woodland grouse, we collated previously published and unpublished data of reproduction in capercaillie and black grouse throughout their ranges from 1930 to 2012. We show that, overall, reproductive success has decreased and stabilized at low levels in most regions whilst capercaillie reproductive output in Scotland is still declining. With today's net reproduction, capercaillie and black grouse adult survival is too low to compensate for reproduction declines. Consequently, populations are expected to further decline unless reproductive performances improve. We put our findings in the context of changes in land use, climate and generalist predator numbers. By critically reviewing how these factors limit reproductive success in capercaillie and black grouse, we hope to shed light on the underlying mechanisms causing the decline. Our results imply that measures should be undertaken to reduce mortality of capercaillie and black grouse chicks and eggs. We suggest that future studies should aim to better understand which predators limit capercaillie and black grouse populations and how predation rates are mediated by continuously changing habitat and climate.

In the boreal forest, the red fox (Vulpes vulpes) is a key species due to its many strong food web linkages and its exploitation of niches that form in the wake of human activities. Recent altitudinal range expansion and a perceived population increase have become topics of concern in Scandinavia, primarily due to the potential impacts of red foxes on both prey and competitor species. However, despite it being a common species, there is still surprisingly little knowledge about the temporal and spatial characteristics of its population dynamics. In this study, we synthesized 12 years of snow-track transect data covering a 27,000-km 2 study area to identify factors associated with red fox distribution and population dynamics. Using Bayesian hierarchical regression models, we evaluated the relationships of landscape productivity and climate gradients as well as anthropogenic subsidies with an index of red fox population size and growth rates. We found that landscapes with high human settlement density and large amounts of gut piles from moose (Alces alces) hunting were associated with higher red fox abundances. Population dynamics were characterized by direct density-dependent growth, and the structure of density dependence was best explained by the amount of agricultural land in the landscape. Population equilibrium levels increased, and populations were more stable, in areas with a higher presence of agricultural lands, whereas density-dependent population growth was more prominent in areas of low agricultural presence. We conclude that human land use is a dominant driver of red fox population dynamics in the boreal forest. We encourage further research focusing on contrasting effects of anthropogenic subsidization on predator population carrying capacities and temporal stability, and potential impacts on prey dynamics.

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