Winter activity patterns of the Black Grouse Tetrao tetrix

Abstract

The winter activity patterns of wild, mostly artificially fed Black Grouse Tetrao tetrix were studied in central western Finland in 1976-82 and 1987-88 . The commencement of the die] activity followed the time of sunrise. For most of the winter, the Black Grouse confined their activity to the morning and spent the rest of the day, 94% on average, in snow roosts . The length of activity was correlated with ambient temperature, but not with photoperiod. In December-February, the activity peaked in the morning, even when snow roosting was not possible . In late March and April, when the snow cover was hard, the activity was clearly bimodal, with the major peak in the morning. In concentrating activity to the morning ("bigeminus" pattern) in winter, Black Grouse differ from most other grouse, which show a major activity peak in the evening. Short diel activity, and snow-roosting and flocking behaviour may constitute a successful energetic and antipredator option in this species.