While collecting birds late in his life along the upper Missouri and Yellowstone Rivers in June 1843, John James Audubon took several specimens of a blackbird he believed was new to science. He named it Quiscalus breweri after Thomas Mayo Brewer, a friend who was a Boston physician and ornithologist. The species had been described previously, however, as Psarocolius cyanocephalus in 1829 by Johannes Wagler; the specific name, meaning blue-headed, is therefore retained by ornithologists, while the English name still honors Brewer. From time to time the bird also has been known locally as "Satin Bird" or "Glossy Blackbird." These colloquial names are rarely used, yet they nicely capture the impression given by sunlit males: their plumage is highlighted by striking violet and blue-green iridescence, punctuated by piercing yellow eyes.
An historically common and conspicuous social species and colonial breeder in open habitats and in farmstead and suburban settings of western North America, Brewer's Blackbird was not recorded nesting east of western Minnesota before 1914. Beginning about then and continuing over the next 4 decades, it undertook a rapid, leap-frog patterned eastward expansion of its breeding range, extending nesting populations approximately 1,200 km at an advancement rate averaging 18 km/year. The pioneering birds took advantage of forest clearing and land conversion to agriculture, and followed linear highway, railroad, and utility corridors to penetrate unfavorable barriers and reach new areas of appropriate breeding habitat. Extension of the species' nesting range also occurred in western Canada, as Brewer's Blackbirds moved 300 km north of their traditional breeding areas to eventually reach southern Mackenzie. Enlargement of the range used by wintering birds occurred concurrently, and now the species is common during winter in the southeastern United States. Today, the Brewer's Blackbird is viewed as a model for understanding avian range expansions promoted by human alterations in habitat.
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