The yellow-headed blackbird, Xanthocephalus xanthocephalus, breeds in prairie and mountain meadow wetland areas of south-central Canada and the central and western United States. Before winter arrives, most individuals migrate southward to southern Arizona, New Mexico, and Mexico, although a few localized populations remain year-round in southern California and Arizona. The yellow-headed blackbird is a common summer resident in the marshes and wetlands of lowland valleys throughout Utah.
The diet of the yellow-headed blackbird varies by season. During the breeding season, it feeds primarily on aquatic insects, and at other times it feeds primarily on grains and seeds. During the summer, fall, and winter, large flocks can be seen foraging in agricultural fields.
Males establish breeding territories before females arrive on the breeding grounds. Males then engage in courtship displays to attract females; as many as six females may nest in one male's territory, and he will mate with each of them.
Each female immediately begins construction of a nest, which is always attached to vegetation above water, after selecting a nesting site within a male's territory. A cup-shaped structure is woven out of wet vegetation and dry grass. As the vegetation dries, it shrinks to create a strong tightly drawn nest. The female incubates her clutch of four eggs for about twelve days, while the male protects the territory against intruders. The young are born naked and blind, and the female takes primary responsibility for feeding them, although the male will sometimes assist in feeding the young. The young leave the nest after about ten days, but they are unable to fly at that time. They do not return to the nest, rather they hide in vegetation for a few days until they are able to fly. Both the male and female continue to feed the young for several days after the chicks leave the nest.