scarce food
20 metres of birch
During winter, the willow grouse eats primarily thin twigs of mountain birch. At the end of the day, its craw is filled with small bits of birch twigs whose total length is 20 metres. This is enough food to last through the night; at daybreak, there is a pile of droppings in the burrow.
Special stomach
The intestinal tract of the willow grouse has a special structure which makes it possible to digest the woody fodder. The bark of the twigs is partially broken down in the small intestine and then taken up by the grouse's body.
Long blind gut
The materials pass from the small intestine into two long blind guts. There, it is broken down by a large quantity of bacteria and becomes easier for the body to absorb. The blind guts become extra long during winter, with a combined length of over one metre.
Anti-grazing poison
Birch twigs contain a poison that protects them against grazing animals. But the willow grouse has a chemical defense which neutralizes the poison. Nevertheless, it refrains from eating the nutritious buds, which are left lying in the snow. This is because the buds contain especially high concentrations of poison.
