Invertebrate Abundance in Different Forest Habitats as Animal Food Available to Capercaillie Tetrao urogallus Chicks

Invertebrate abundance was estimated in 1981 and 1982 by sweep-netting at twelve forest vegetation types in Vegarshei, Southern Norway. Invertebrates are expected to be a major determinant of habitat quality to gallinaceous birds, since animal food is considered essential to young chicks. The twelve fixed stations were chosen to illustrate poor and rich habitats and a gradient from bog to forest habitat. Rich vegetation types also had the highest abundance of invertebrates mainly due to moist and heavy soils. A comparison between a clear-cutting and a similar vegetation type not logged, showed strong reduction in invertebrate availability after cutting. The influence of this alteration on availability of the capercaillie Tetrao urogallus chicks' food is discussed.