Magpies are omnivorous and thus are able to eat both plant and animal matter. They primarily prey on insects and other animals, including carrion, small mammals such as mice, smaller bird species and the young and eggs of other birds.
Magpies are historically associated with bison herds, as they provide a service to the animal by picking off ticks and other parasitic bugs from the animals' coats. Their diets change with the season, as magpies take advantage of any available source of food and adapt to eating fruits and nuts when available. Though the birds do eat plant matter, 70 percent or more of their diet consists of animal-based matter.