Spring social organisation, habitat use, diet, and body mass dynamics of hazel grouse Bonasa bonasia in northeastern Asia

Hazel grouse Bonasa bonasia encounter more severe climates in northeastern Asia than anywhere else in their range, yet the time between snow melt and laying is shorter here than elsewhere. Birds were able to lay early because they moved to follow the phenology of snow melt, changing their diet as they did so. Before snow melt, habitat distribution and diet were the same as in winter. As soon as the first snow‐free patches occurred on terraces, grouse moved there and fed on thawed berries, which were available in great quantities on these terraces only. This habitat shift coincided with the shift in diet; winter foods such as twigs, buds and catkins decreased from 75 to 3%, whereas the proportion of berries increased from 6 to 70%. Females began to lay a few days after all snow had melted, returning to riparian habitats where the variety and abundance of plants were greatest. Foliage increased from 27 to 72% of the diet, and the proportion of berries declined from 70 to 19%. In winter, Asian hazel grouse primarily occur in flocks. In spring males guard their mates rather than their territories; they follow females up to a few kilometres from their riparian breeding habitats, as these move on to terraces to gain weight for egg laying. Such food related movements between habitats have not been reported for this species in Europe.