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Documents disponibles écrits par cet auteur (10)
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Article
Risto Tornberg, Auteur ; Seppo Rytkönen, Auteur ; Panu Välimäki, Auteur ; Jari Valkama, Auteur ; Pekka Helle, AuteurAround the nests of many birds of prey the pressure of nest predators is decreased. This attracts other bird species to breed near nests of those birds of prey in order to benefit from protection conferred. This study examines the possible prote[...]
Article
Risto Tornberg, Auteur ; Seppo Rytkönen, Auteur ; Panu Välimäki, Auteur ; Jari Valkama, Auteur ; Pekka Helle, AuteurAround the nests of many birds of prey the pressure of nest predators is decreased. This attracts other bird species to breed near nests of those birds of prey in order to benefit from protection conferred. This study examines the possible prote[...]
Article
Katri Korpela, Auteur ; Pekka Helle, Auteur ; Heikki Henttonen, Auteur ; Erkki Korpimäki, Auteur ; Esa Koskela, Auteur ; Otso Ovaskainen, Auteur ; Hannu Pietiäinen, Auteur ; Janne Sundell, Auteur ; Jari Valkama, Auteur ; Otso Huitu, AuteurThe 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, whi[...]
Article
Saija Sirkia, Auteur ; Ari Nikula, Auteur ; Pekka Helle, Auteur ; Harto Linden, Auteur ; Kai Norrdahl, Auteur ; Petri Suorsa, Auteur ; Pentti Valkeajarvi, AuteurCapercaillie (Tetra urogallus) has traditionally been considered an old forest-dependent species. The lekking sites especially, were thought to be located in older forests. We studied the persistence of Capercaillie lekking areas in relation to [...]
Article
Saija Sirkia, Auteur ; Andreas Linden, Auteur ; Pekka Helle, Auteur ; Ari Nikula, Auteur ; Jonas Knape, Auteur ; Harto Linden, AuteurIn Finland, Capercaillie (Tetrao urogallus) populations have a history of serious decrease starting from the mid-20th century. The decline is temporally in line with the expansion of modern forestry practices that created major changes in the la[...]
Article
Osmo Ratti, Auteur ; Ulriikka Ojanen, Auteur ; Pekka Helle, AuteurBlack flies (Simuliidae) have been observed to harass Black Grouse (Tetrao tetrix) in northern Finland during summer. We studied experimentally whether group size affects the attack rate of black flies on Black Grouse. The increase in flock size[...]
Article
Saija Sirkia, Auteur ; Pekka Helle, Auteur ; Harto Linden, Auteur ; Ari Nikula, Auteur ; Kai Norrdahl, Auteur ; Petri Suorsa, Auteur ; Pentti Valkeajarvi, AuteurWe studied the effects of habitat loss, fragmentation and their interaction on the persistence of Capercaillie lekking areas at three study areas in Finland. We inspected a total of 381 leks twice with an interval of 10-30 years, and classified [...]
Article
Marja Isomursu, Auteur ; Osmo Ratti, Auteur ; Pekka Helle, Auteur ; Tuula Hollmen, AuteurParasite infections are often more common in male vertebrates than in females. Sexual selection leading to dimorphism can cause sexual differences in immune defence, behaviour or body size. Possible proximate explanations for male bias in parasi[...]
Article
Marja Isomursu, Auteur ; Osmo Ratti, Auteur ; Tuija Liukkonen, Auteur ; Pekka Helle, AuteurInbreeding can have a negative influence on several life-history traits as well as disease resistance in birds and mammals through different genetic mechanisms. Endangered and declining populations may be at particular risk for inbreeding. The l[...]
Article
Marja-Liisa Kaisanlahti-Jokimäki, Auteur ; Jukka Jokimäki, Auteur ; Esa Huhta, Auteur ; Maarit Ukkola, Auteur ; Pekka Helle, Auteur ; Tuomo Ollila, AuteurWe examined the potential effects of tourist destinations on territory occupancy and breeding success of the Golden Eagle (Aquila chrysaetos) in northern Finland. We gathered information from 12 tourist destinations and from all known Golden Eag[...]
