Tuesday, September 1, 2015

Green Heron

Fortunately, John Holden and I were wearing our hats when we spied this Green Heron in Rice County, Minnesota, last Wednesday. This little heron goes by many names, including “Shite-polk,” due to its habit of defecating as it flies from its perch.

Green Herons have other names too, including Green-backed, Striated, and Little Green heron, due to ornithologists’ confusion about the species' systematics. This situation is not surprising. The birds’ range is huge—North and South America, Africa, and Asia. At least 33 races are recognized, and scientists argue that some are, in fact, distinct species. For example, Martinez-Vilalta et al. (2014) consider all these populations to be subsets of a single species, the Green-backed Heron. Davis and Kushlan (1994) follow the current American Ornithologists’ Union edict that the North American population is a distinct species, the Green Heron, distinct from South America’s Striated Heron. This unlikely conclusion leaves the South American birds more closely related to Old World populations than to North American birds.

When Erika and I visited the Galapagos Islands, we saw Lava Herons, like the one in the photo below. This population looks like very dark Green Herons. These birds may be another species in the Green Heron complex. Most ornithologists, however, consider them to be a dark morph of the South American birds. They are variable in color—this one is a bit paler than most—and no significant genetic differences have been found between Galapagos and mainland Striated Herons.

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