HABITAT SEPARATION BY SYMPATRIC FOREST GROUSE IN FENNOSCANDIA IN RELATION TO BOREAL FOREST SUCCESSION

Sympatric forest grouse in intensively managed conifer-dominated fores ts of the southern boreal zone in Sweden occupied different forest suc cessional stages. Black grouse (Tetrao tetrix) selected forest stands 0 - 20 years old, hazel grouse (Bonasa bonasia) selected those 20 - 50 years old, and capercaillie (Tetrao urogallus) selected those greater -than-or-equal-to 90 years old. Moreover, hazel grouse also selected s tands with 1 - 10% deciduous trees, whereas capercaillie selected stan ds with no deciduous trees. The relative numbers of each grouse specie s were similar in two areas of intensively managed industrial forest, but differed in an area where forestry was less intensive and where fo rests had old-growth characteristics, i.e., they were old and multilay ered. Black grouse dominated in the intensively managed areas, whereas hazel grouse dominated in the less intensively managed area. We sugge st that under natural conditions, black grouse inhabited the early-suc cessional stages of forest following burns, hazel grouse inhabited the next, denser, successional stage and also old-growth spruce-dominated forests in fire refugia, and capercaillie inhabited stands of open, o ld, pine-dominated forest maintained by forest fire. The black grouse appears to be preadapted to the modern system of clearcut forest manag ement. However, this system is clearly detrimental to the hazel grouse and capercaillie. To maintain all three species in a managed landscap e, forest managers must strive to mimic more closely the natural varia tion in types and sizes of forest stands.