This species prefers generally open habitats with clumps of trees. It can therefore be found in farmlands and suburban areas, where it comes into regular contact with people. Where persecuted it becomes very wary, but otherwise it is fairly tolerant of human presence. Historically associated with bison herds, it now lands on the backs of cattle to glean ticks and insects from them. Large predators such as wolves are commonly followed by black-billed magpies, who scavenge from their kills. The species also walks or hops on the ground, where it obtains food items such as beetles, grasshoppers, worms, and small rodents.
The black-billed magpie is one of the few North American birds that build a domed nest, which is made up of twigs and sits near the top of trees, usually housing 6–7 eggs. Incubation, by the female only, starts when the clutch is complete, and lasts 16–21 days. The nestling period is 3–4 weeks.
