Northern Harrier Taxonomy Question (1 Viewer)

[Hen Harrier] Often treated as conspecific with Northern Harrier, but adults of latter are intermediate in various respects between Palearctic Hen Harrier and Neotropical Cinereous Harrier, and juveniles of Hen differ markedly from those of American forms. All three are geographically isolated and could be considered distinct races of one species, or three species forming a superspecies, which is the course followed here...

It is more customary to regard the Holarctic pair as one species and cinereus as another that is 'perhaps conspecific' (Amadon & Bull 1988). They are similar in structure and habits, and largely confined to temperate and cold climates (Nieboer 1973), but, with geographical isolation, have developed significant plumage differences. In a number of ways, hudsonius is more like cinereus than like cyaneus: for example, the males of both New World forms are closer to each other than to cyaneus in having less extensive black on the tips of the outer five primaries, more tail-barring, and rufous or blackish markings on the white underbody and wing-linings; females and immatures are also more clearly distinct from each other in the American forms.

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Abstract
The Hen Harrier Circus c. cyaneus and Northern Harrier C. cyaneus hudsonius are classified as conspecifics by some modern authors and as separate species by others. The tendency to treat the two as conspecifics may have its origin in erroneous nineteenth-century illustrations, and their allopatry has meant that twentieth-century adherence to the Biological Species Concept has hindered attempts to classify them to universal approval. This dichotomy of opinion is a hindrance to our understanding of both harriers, and may adversely affect their conservation.

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Systematics: Related Species:
Old World and New World populations of C. cyaneus differ enough genetically, likely simply by virtue of having allopatric breeding ranges, that some have suggested they deserve to be treated as separate species (Simmons 2000, Ferguson-Lees and Christie 2001, Wink and Sauer-Gurth 2004). Some authorities have included C. cinereous [sic], the Cinereous Harrier of southern Central America, in C. cyaneus or grouped the two species into a superspecies (e.g., Amadon and Short 1976), but molecular phylogenetics imply that this species is distantly related to C. cyaneus (Wink and Sauer-Gurth 2004).

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Peter Kovalik said:

Proposal (776) to SACC

Treat New World Circus (c.) hudsonius as a separate species from Old World Circus cyaneus

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