Responses by the capercaillie Tetrao urogallus, and the willow grouse Lagopus lagopus, to the green matter available in early spring

Abstract

Food matter eaten in the first snowless spots early in the spring by capercaillie Tetrao urogallus and willow grouse Lagopus lagopus was studied in Finnish Forest Lapland. When the snow disappears, both species change to feeding mainly on the plants available in the snowless spots, although male capercaillie does not exploit this nutritious diet to the same extent as female capercaillie and willow grouse. Selection in favour of nitrogen and phosphorus‐rich food items, i.e. Betula pubescens, male catkins Eriophorum vaginatum, flower buds, and Equisetum spp., stems and tips, seems to be characteristic especially of the female capercaillie, whose winter diet is poor in these elements. Female capercaillie also feeds on more plant species or different parts of plants at one time than willow grouse, while no differences were recorded between male and female willow grouse in the composition of their spring food. The crowberry Empetrum hermaphroditum, almost regularly produces a bountiful berry crop in northern Finland, and since it overwinters well, it represents an easy source of energy and water available almost every spring. The quality and/or the quantity of the green food matter available early in the spring may fluctuate considerably and be of importance for short‐term fluctuations in the populations of these tetraonid species.

Patterns in grouse and Woodcock Scolopax rusticola hunting yields from central Norway 1901–24 do not support the alternative prey hypothesis for grouse cycles

“…1977, Slagsvold & Grasaas 1979. The most important factor for grouse in spring is probably snow cover, which influences the availability of high-quality food prior to egg-laying (Slagsvold & Grasaas 1979, Pulliainen & Tunkkari 1991, but temperatures may also be of interest, by affecting plant phenology and insect population growth, important for grouse chicks. Weather in June, after hatching, also seems to be important for grouse chick survival (Slagsvold & Grasaas 1979, Erikstad & Spidsø 1982, Hanssen & Utne 1985, Steen et al .…”

Habitat selection and diet of the Capercaillie Tetrao urogallus in Abernethy Forest, Strathspey, Scotland

“…Pulliainen & Tunkkari (1991) have noted the importance of a high nitrogen and phosphorus diet (male catkins of Downy Birch Betula pubescens, flower buds of Eriophorum vaginatum and stems and tips of horsetails Equisetum sp.) prior to egg-laying in Capercaillie, but the pollen cones develop too late for this.…”

“…Broadleaved trees were once more common in the ancient native pinewoods of eastern Scotland but were selectively cut for firewood and charcoal or regarded as 'weeds' (Steven & Carlisle 1959, Summers et al 1999. It would seem that the introduction of broadleaved trees, particularly Aspen Populus tremula (Rolstad 1988b) and birch, might benefit Capercaillie by providing spring food (Pulliainen & Tunkkari 1991).…”

Vulnerability of black grouse hens to goshawk predation: result of food supply or predation facilitation?

“…Before and during egg laying, females prefer to feed on nutritious plants and parts of plants like the buds of the cottongrass Eriophorum spp., new shoots of forbs and shrubs like the bilberry Vaccinium myrtillus, etc. (Pulliainen and Tunkkari 1991). The availability of such high-quality food may vary between years due to temperature and snow conditions of the spring (Siivonen 1957) or inherent fluctuations in plant quality (Tast and Kalela 1971;Laine and Henttonen 1983;Selås 2003).…”