We studied experimentally how heterospecific attraction may affect habitat selection of migrant p... more We studied experimentally how heterospecific attraction may affect habitat selection of migrant passerine birds in Finnish Lapland. We manipulated the densities of resident tit species (Parus spp.). In four study plots residents were removed before the arrival of the migrants in the first study year, and in four other plots their densities were increased by releasing caught individuals. In the second year the treatments of the areas were reversed, allowing paired comparisons within each plot. We also investigated the relative abundance of arthropods in the study plots by the sweep-net method. This allowed us to estimate the effect of food resources on the abundance of birds. The heterospecific attraction hypothesis predicts that densities of migrant species (especially habitat generalists) would be higher during increased resident density. Results supported this prediction. Densities and number of the most abundant migrant species were significantly higher when resident density was ...
We investigated whether different species of birds associated with each other while foraging duri... more We investigated whether different species of birds associated with each other while foraging during the breeding season. On average 50% of foraging observations were in mixed-species foraging aggregations, but with extensive interspecific variation. The occurrence ...
Top predators may induce extensive cascading effects on lower trophic levels, for example, throug... more Top predators may induce extensive cascading effects on lower trophic levels, for example, through intraguild predation (IGP). The impacts of both mammalian and avian top predators on species of the same class have been extensively studied, but the effects of the latter upon mammalian mesopredators are not yet as well known. We examined the impact of the predation risk imposed by a large avian predator, the golden eagle (Aquila chrysaetos, L.), on its potential mammalian mesopredator prey, the red fox (Vulpes vulpes, L.), and the pine marten (Martes martes, L.). The study combined 23 years of countrywide data from nesting records of eagles and wildlife track counts of mesopredators in Finland, northern Europe. The predation risk of the golden eagle was modeled as a function of territory density, density of fledglings produced, and distance to nearest active eagle territory, with the expectation that a high predation risk would reduce the abundances of smaller sized pine martens in p...
Proceedings. Biological sciences / The Royal Society, Jan 22, 2014
The cyclic population dynamics of vole and predator communities is a key phenomenon in northern e... more The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data collected throughout Finland during 1986-2011, we analyse the spatio-temporal variation in the interactions between populations of voles and specialist, generalist and avian predators, and investigate by simulations the roles of the different predators in the vole cycle. We test the hypothesis that vole population cyclicity is dependent on predator-prey interactions during winter. Our results support the importance of the small mustelids for the vole cycle. However, weakening specialist predation during winters, or an increase in generalist predation, was not associated with the loss of cyclicity. Strengthening of delayed density dependence...
... SAMI KURKI\ ARI NIKULA$\ PEKKA HELLE% and HARTO LINDEłN& Laboratory of Ecology an... more ... SAMI KURKI\ ARI NIKULA$\ PEKKA HELLE% and HARTO LINDEłN& Laboratory of Ecology and Animal Systematics\ Department of Biology\ University of Turku\ FIN!19903 Turku\ Finland^ $Finnish Forest Research Institute\ Rovaniemi Research Station\ PO Box 05\ FIN!85290 ...
Background/Question/Methods Top predators may induce extensive cascading effects on lower trophic... more Background/Question/Methods Top predators may induce extensive cascading effects on lower trophic levels, e.g. implicitly through intraguild predation, where predatory species compete over shared prey but also prey on each other. The predation impacts of both mammalian and avian top predators on the species of the same guild have been widely studied, whereas the effects of raptors upon mammalian mesopredators are not well known. We examined the impacts of the predation risk of a large avian predator, the golden eagle (Aquila chrysaetos), upon the abundance of its potential mammalian mesopredator prey in Finland, northern Europe. The study combined 23 years of unique, countrywide data from nesting records of eagles and wildlife track counts of mesopredators. To assess changes in abundance of red foxes (Vulpes vulpes) and pine martens (Martes martes), the predation risk of golden eagle was modelled either through territory density, density of fledglings produced or distance to the nea...
We studied experimentally how heterospecific attraction may affect habitat selection of migrant p... more We studied experimentally how heterospecific attraction may affect habitat selection of migrant passerine birds in Finnish Lapland. We manipulated the densities of resident tit species (Parus spp.). In four study plots residents were removed before the arrival of the migrants in the first study year, and in four other plots their densities were increased by releasing caught individuals. In the second year the treatments of the areas were reversed, allowing paired comparisons within each plot. We also investigated the relative abundance of arthropods in the study plots by the sweep-net method. This allowed us to estimate the effect of food resources on the abundance of birds. The heterospecific attraction hypothesis predicts that densities of migrant species (especially habitat generalists) would be higher during increased resident density. Results supported this prediction. Densities and number of the most abundant migrant species were significantly higher when resident density was ...
We investigated whether different species of birds associated with each other while foraging duri... more We investigated whether different species of birds associated with each other while foraging during the breeding season. On average 50% of foraging observations were in mixed-species foraging aggregations, but with extensive interspecific variation. The occurrence ...
Top predators may induce extensive cascading effects on lower trophic levels, for example, throug... more Top predators may induce extensive cascading effects on lower trophic levels, for example, through intraguild predation (IGP). The impacts of both mammalian and avian top predators on species of the same class have been extensively studied, but the effects of the latter upon mammalian mesopredators are not yet as well known. We examined the impact of the predation risk imposed by a large avian predator, the golden eagle (Aquila chrysaetos, L.), on its potential mammalian mesopredator prey, the red fox (Vulpes vulpes, L.), and the pine marten (Martes martes, L.). The study combined 23 years of countrywide data from nesting records of eagles and wildlife track counts of mesopredators in Finland, northern Europe. The predation risk of the golden eagle was modeled as a function of territory density, density of fledglings produced, and distance to nearest active eagle territory, with the expectation that a high predation risk would reduce the abundances of smaller sized pine martens in p...
Proceedings. Biological sciences / The Royal Society, Jan 22, 2014
The cyclic population dynamics of vole and predator communities is a key phenomenon in northern e... more The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data collected throughout Finland during 1986-2011, we analyse the spatio-temporal variation in the interactions between populations of voles and specialist, generalist and avian predators, and investigate by simulations the roles of the different predators in the vole cycle. We test the hypothesis that vole population cyclicity is dependent on predator-prey interactions during winter. Our results support the importance of the small mustelids for the vole cycle. However, weakening specialist predation during winters, or an increase in generalist predation, was not associated with the loss of cyclicity. Strengthening of delayed density dependence...
... SAMI KURKI\ ARI NIKULA$\ PEKKA HELLE% and HARTO LINDEłN& Laboratory of Ecology an... more ... SAMI KURKI\ ARI NIKULA$\ PEKKA HELLE% and HARTO LINDEłN& Laboratory of Ecology and Animal Systematics\ Department of Biology\ University of Turku\ FIN!19903 Turku\ Finland^ $Finnish Forest Research Institute\ Rovaniemi Research Station\ PO Box 05\ FIN!85290 ...
Background/Question/Methods Top predators may induce extensive cascading effects on lower trophic... more Background/Question/Methods Top predators may induce extensive cascading effects on lower trophic levels, e.g. implicitly through intraguild predation, where predatory species compete over shared prey but also prey on each other. The predation impacts of both mammalian and avian top predators on the species of the same guild have been widely studied, whereas the effects of raptors upon mammalian mesopredators are not well known. We examined the impacts of the predation risk of a large avian predator, the golden eagle (Aquila chrysaetos), upon the abundance of its potential mammalian mesopredator prey in Finland, northern Europe. The study combined 23 years of unique, countrywide data from nesting records of eagles and wildlife track counts of mesopredators. To assess changes in abundance of red foxes (Vulpes vulpes) and pine martens (Martes martes), the predation risk of golden eagle was modelled either through territory density, density of fledglings produced or distance to the nea...
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