The common and widespread Bullock's Oriole (Icterus bullockii) breeds in western North America from southern Canada south to northern Mexico. It winters mainly from Mexico south to Guatemala, with small numbers found along the Gulf coast of the southeastern United States from Texas to southern Georgia and Florida. It is found in summer along forest edges and in isolated groves and streamside woods, especially in cottonwood trees. Its habits appear to be similar to those of the Baltmore Oriole (Icterus galbula).
As a result of frequent hybridization between the Bullock's and Baltimore Orioles where their ranges meet in the Great Plains, these two orioles were at one time treated as conspecific (i.e., members of the same species), representing two forms of a species that was known as the Northern Oriole. However, genetic studies have indicated that these two species are not even each other’s closest relatives (for a full discussion of this issue, see Jacobsen and Omland 2011).
(Kaufman 1996; AOU 1998)
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