We examined the breeding success of forest grouse in relation to anthropogenic forest fragmentation in Finland. Employing Geographic Information Systems (GIS) and grouse data derived from Finnish wildlife triangle censuses conducted during 1989–1994, we combined the locations of 2267 Black Grouse (Tetrao tetrix) and 1060 Capercaillie (T. urogallus) females after the breeding season in mid‐August with landscape data. The indicators of breeding success were the proportion of grouse hens with a brood and brood size. Two study areas (each 45 000 km2) in the boreal zone were selected for investigation. The breeding success of grouse was negatively correlated with both fragmentation of forest area per se by farmland and the decreasing proportion of older forest as a result of clear‐cutting. The extent of landscape accounting best for variation in nesting success was an order of magnitude larger (∼100 km2) than the area most probably used by a grouse female and her brood during the summer, which suggests that landscape‐scale factors may override local factors such as track size and distance from edge. The proportion of grouse hens with a brood was lower in heavily fragmented landscapes than in more continuous forest landscapes whereas only minor differences in brood size were detected. We suggest that the most likely cause of the observed spatial correlation was higher nest predation by generalist predators in fragmented forest landscapes. The effects of landscape composition on the breeding success of grouse were more marked in northern than in southern Finland, probably because predator populations are more food‐regulated in the north. The diminished breeding success of forest grouse as a result of increased forest fragmentation is a probable cause of population declines in forest grouse species during the past decades in Fennoscandia.

Summary 0[ The e}ects of human!caused fragmentation of boreal forest on the abundance of red fox Vulpes vulpes L[ and pine marten Martes martes L[ were studied by combining the Finnish wildlife!triangle snow!track data "0889Ð83# with land!use and forest resources data employing the GIS[ Two study areas "each 34 999 km 1 # located in northern and southern Finland were selected for the investigation[ 1[ The extent of landscape that best explained predator abundance "tracks per 09 km 13 h −0 # was the same "about 099 km 1 # in both species and study areas[ 2[ The decreasing proportion of older forest and the increasing proportions of young forest and agricultural land in the landscape positively a}ected track density of red fox[ The relationship between agricultural land and fox abundance\ however\ was characterized by a convex curve peaking at 19Ð29) of agricultural land[ With the habitat classi_cation used\ landscape composition explained 15) and 00) of the spatial variation in fox abundance in the northern and southern study area\ respec! tively[ 3[ The relationship between landscape composition and pine marten abundance was not as clear as in that of red fox[ Landscape composition explained 09) and 5) of spatial variation in pine marten abundance in the northern and southern study area\ respectively[ In both areas a positive impact occurred with the increasing proportion of young forest in the landscape\ but in the northern area the negative e}ect of increasing proportion of agricultural land was dominant[ 4[ The abundances of red fox and pine marten were not negatively correlated\ indi! cating that competition or intraguild predation by red fox do not determine abundance of pine marten on a landscape scale[ 5[ A general increase in predation pressure by generalist predators in fragmented forest landscapes has been an intensively discussed conservation problem during recent years[ We conclude that the red fox is a species potentially able to cause elevated predation pressure in boreal landscapes fragmented by human activities\ but that the evidence against the pine marten is weaker[ Key!words] Finland\ forest fragmentation\ geographical information systems\ land! scape ecology\ predation[ Journal of Animal Ecology "0887# 56\ 763Ð775

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. We studied temporal and spatial synchrony of population fluctuations in the capercaillie (Tetrao urogallus), the black grouse (Tetrao tetrix) and the hazel grouse (Bonasa bonasia) in Finland. 2. The data consist of route censuses (20 000-30 000 km annually) performed in 11 provinces during 1964-83. The population data for the three species in each province were standardized to zero mean and unit variance. 3. Cross-correlation analysis indicates that population dynamics of the three species in every area are in rather good temporal synchrony. Moreover, with the aid of kmeans clustering, the 11 provinces could be merged into four regions, indicating largescale synchrony in dynamics of the three tetraonid species. 4. Because it is obvious that this synchrony cannot be due only to the similar life histories of these species, we explored whether it could be influenced by a common synchronizing factor affecting all the species simultaneously. In order to do this we used a Leslie matrix-based simulation approach. In this model there is a stochastic hit of breeding failure at a given average interval. This failure was shown to synchronize the population dynamics of the species with primarily different life tables.

Summary1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems. 2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels. 3. We use the recolonization of a top predator in a three-level boreal ecosystem as a natural experiment to test if large-scale biomass distributions and population trends support MRH. Inspired by EEH, we also test if top-down interference and bottom-up productivity impact regional ecosystem structures. 4. We use data from the Finnish Wildlife Triangle Scheme which has monitored top predator (lynx Lynx lynx), mesopredator (red fox Vulpes vulpes) and prey (mountain hare Lepus timidus) abundance for 17 years in a 200 000 km 2 study area which covers a distinct productivity gradient. 5. Fox biomass was lower than expected from productivity where lynx biomass was high, whilst hare biomass was lower than expected from productivity where fox biomass was high. Hence, where interference controlled fox abundance, lynx had an indirect positive impact on hare abundance as predicted by MRH. The rates of change indicated that lynx expansion gradually suppressed fox biomass. 6. Lynx status caused shifts between ecosystem structures. In the 'interference ecosystem', lynx and hare biomass increased with productivity whilst fox biomass did not. In the 'mesopredator release ecosystem', fox biomass increased with productivity but hare biomass did not. Thus, biomass controlled top-down did not respond to changes in productivity. This fulfils a critical prediction of EEH. 7. We conclude that the cascade involving top predators, mesopredators and their prey can determine large-scale biomass distribution patterns and regional ecosystem structures. Hence, interference within trophic levels has to be taken into account to understand how terrestrial ecosystem structures are shaped.

Temporal asymmetry in patterns of regional climate change may jeopardize the match between the proximate and ultimate cues of the timing of breeding. The consequences on short-and long-term population dynamics and trends as well as the underlying mechanisms are, however, often unknown. Using long-term data from Finland, we demonstrate that black grouse (Tetrao tetrix) have responded to spring warming by advancing both egg-laying and hatching. However, early summer (the time of hatching) has not advanced, and chicks have to face colder post-hatching conditions. Demonstrating that these conditions are critical to post-hatching survival, we show that chicks are increasingly suffering higher mortality because they hatch too early. Consequently, breeding success and population size has severely declined over the past four decades. Finally, we modelled the impact of this particular climate change scenario on population dynamics and show that the mismatch can further explain the observed collapse of cyclic fluctuations. Because the evolutionary response of grouse is lagging behind the novel selective pressures, seasonally asymmetric climate change is likely to constitute an important determinant of future short-and long-term changes in the dynamics of black grouse populations.

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