Does fragmentation by logging reduce grouse reproductive success in boreal forests?

Abstract

In 1999 and 2001, we compared the population characteristics of capercaillie Tetrao urogallus, black grouse T. tetrix and hazel grouse Bonasa bonasia inside the pristine forest reserve State Natural Reserve ‘Pinezhskiy’ in northwestern Russia and in the logged forests surrounding the reserve. We also compared the abundance of mammalian predators and birds of prey. The August density of capercaillie was lower in logged forests than in the reserve (P = 0.05), but black grouse tended to be more abundant in the logged area (P = 0.08). For hazel grouse, no difference in abundance was found between the reserve and the logged area. Reproductive success of all three grouse species was generally higher in the logged area than in the reserve. A winter track survey indicated low abundance (< 1 track/10 km/24 hours) and no difference in density of small and mediumsized mammalian predators between the reserve and the logged area. The only exception was red fox Vulpes vulpes whose tracks were recorded only in the logged area. Buzzards Buteo spp. and goshawk Accipiter gentilis were the most numerous birds of prey. Goshawk tended to be more common in the reserve (P = 0.09), whereas buzzards were seen more often in the logged area (P = 0.1). Tracks of mountain hare Lepus timidus was twice as abundant in the logged forest (P = 0.02), whereas tracks of red squirrel Sciurus vulgaris was almost 10 times more numerous in the reserve (P < 0.001) than in the logged area. Judged by the remains found, the majority (72%) of grouse were killed by birds of prey. Our study suggests that reproduction of all three species of forest grouse in this region remains stable or increases following logging. We hypothesise that this may be due to the type of logging performed and to differences in the composition of predators and of prey other than grouse inside and outside the reserve.

Kin groups in closely spaced capercaillie leks

“…Capercaillie occur in moderately high numbers, at a density of ca. five birds per km 2 in August (Borchtchevski et al 2003), with >20 leks regularly distributed across the continuous, forested landscape. The three study leks were located next to one another in the central part of the reserve, with an estimated 12-14 males at one lek (henceforth termed lek 12) and >25 attending males at each of the other two (henceforth leks 17 and 32) .…”

Goshawk breeding densities in relation to mature forest in southeastern Norway

“…Forest grouse, i.e., Capercaillie (Tetrao urogallus), Black Grouse (T. tetrix) and Hazel Grouse (Bonasa bonasia), which in Fennoscandia have showed declines similar to that of the Goshawk (Lindströ m, 1994;Tornberg et al, 1999), have traditionally been regarded as the most important prey items (Tornberg et al, 2006). However, since the long-term decline in grouse populations cannot solely be explained by direct or indirect negative effects of modern forest management (Lindströ m, 1994;Borchtchevski et al, 2003), a better understanding of the influence of forestry on Goshawk numbers is required.…”

Declining reproductive output in capercaillie and black grouse – 16 countries and 80 years

“…However, chicks of both species may be vulnerable to low insect abundance because invertebrates are an important source of protein during the first couple of weeks after hatching (Rajala, 1959;Atlegrim & Sjöberg, 2008;Wegge & Kastdalen, 2008) and food limitation may predispose chicks to predation. Predation is the dominant proximate cause of losses of woodland grouse eggs, chicks and adults (Hagen, 1952;Hörnfeldt, 1978;Angelstam, 1984;Storaas & Wegge, 1987;Kurki et al, 1997;Borchtchevski et al, 2003;Wegge & Kastdalen, 2007;Ludwig et al, 2010;Wegge & Rolstad, 2011;Åhlen et al, 2013). Mammalian predation has also been shown, in both experimental and correlative studies, to play an important role in short-term grouse population dynamics in the sense that predators predominantly limit reproduction and thus population growth rates (Marcström et al, 1988;Lindström et al, 1994;Kurki et al, 1997;Kauhala et al, 2000;Summers et al, 2004).…”

“…In Scotland, forest maturation is suggested to accelerate black grouse declines by reducing brood-rearing and nesting habitat following canopy closure (Pearce-Higgins et al, 2007). These man-made habitat changes may also affect mortality indirectly by altering the distribution and composition of predators in the landscape (Borchtchevski et al, 2003). Likewise, changes in habitat can affect predator-prey relationships by making predators more efficient in locating and killing grouse through edge-related effects (Andren & Angelstam, 1988).…”