Adult birds are primarily vegetarian. The animal matter in the diet is mostly taken accidentally with plant food.
What they eat
They tend to feed on the ground, but during the winter can forage in shrubs or trees.
Main foods vary locally and seasonally, and include buds, needles and cones of pines, catkins and other parts of birch, various dwarf shrubs, grasses and berries, with heather and bilberry of particular importance.
For the first few days of their life, chicks take mainly spiders and insects. Moth caterpillars and sawfly larvae are particularly important and often form the bulk of the diet. The proportion of plant matter in the diet increases with age, and by the time the young are independent they rely on a predominantly plant diet.