Migration Info This western counterpart to the eastern Baltimore Oriole moves rapidly up the west coast, often reaching the California-Oregon border by mid-April. In the easterly portions of its range, arrivals are up to two weeks later than at the same latitude along the coast. During the winter, this species is most numerous along the Pacific slope of Mexico, where it feeds heavily on nectar. The migratory characteristics of the Bullock's Oriole are poorly understood; the birds are believed to move primarily at night in small flocks. Mature males arrive first, followed by females and first-year males.