Bird subspecies

Distinguishing Eurasian and American Common Merganser

The Eurasian subspecies group of Common Merganser, known by the English name Goosander, has occurred numerous times in the Aleutian Islands of western Alaska, but has never been identified farther east in North America. The American subspecies has some potential to wander to Eurasia, but has never been recorded there. I’ve never seen any in-depth …

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The Newfoundland Moorhen was an American based on back color

Last winter’s Common Moorhen in Newfoundland, given the likely split of New World and Old World moorhens into separate species, led me to try to determine the origin of the Newfoundland bird. That study of photos turned up a few small differences in bill color and shape, but nothing fully reliable. Now I have finally …

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Distinguishing Interior West from Western Taiga White-crowned Sparrows

See my detailed discussion of White-crowned subspecies here, which needs updating with the information below. In early May 2011 I spent several days in southeastern Arizona, and devoted a lot of time to studying the White-crowned Sparrows. At that date most of them were migrant Interior West birds of subspecies Z. l. oriantha. Most of …

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Intergradation between Mexican Duck and Mallard in Arizona

The Mexican Duck was formerly considered a species (Anas diazi), and is currently lumped with Mallard (as subspecies Anas platyrhynchos diazi), but recent DNA studies suggest that Mottled Duck (not Mallard) is its closest relative (McCracken et al. 2001). Whatever its genetic background, it is clear from field observations that Mexican Ducks and Mallards interbreed …

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Three interesting Brant from Massachusetts

Note: I’m preparing posts on the range and identification of Brant subspecies, which will help make the following more understandable to those who are not already well-versed in the intricacies of Brant. Over the last fifteen or so years I have seen several odd “gray-bellied” Brant along the US Atlantic coast. This spring I finally …

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Identifying subspecies by behavior – Savannah Sparrow

Identifying subspecies adds richness to your birding by adding another layer of understanding. What’s more, during spring migration, behavior can offer a quick and fairly reliable clue to use when distinguishing local breeders from migrants. This is simply an extension of a bit of advice often given for identifying shorebirds: to watch for birds around …

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Distinguishing Green-winged and Common Teal

The Green-winged Teal (known as Common Teal in English-speaking parts of Eurasia) is currently considered a single species by the AOU, but two subspecies are distinctive in adult male plumage and are split into two species by many authorities. Green-winged Teal (American) – Anas crecca carolinensis Common Teal (Eurasian) – Anas crecca crecca ((Common Teal nests in …

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Distribution of Greater White-fronted Goose subspecies

The Greater White-fronted Goose (Anser albifrons) occurs throughout much of North America, but is found in largely disjunct populations. Only two North American subspecies are listed by Ely and Dzubin (1994), four by Pyle (2008), but five well-defined “population units” have occurred in North America, and there may be more. Banks (2011) recognizes four of …

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