Pikas like to eat grass or flowers. Pikas enjoy eating willows and sedges the most. If there is very little grass around they have been known to eat dead birds. You can find more information here: http://www.taiga.net/yourYukon/col105.html
Pikas eat grass, forbs and seeds. They are herbivore animals and like to wander around all day collecting things and slide on the rocks. They look like mice.