Dark-eyed Junco intergrade ('Slate-coloured Junco' x 'Oregon Junco'), Jackson State Park, Morgan County (Colorado, USA), 1st December 2012 - copyright Steve Mlodinow
(photo ID: 1244)
Where the ranges of Slate-coloured Junco and Oregon Junco overlap (e.g. in Alberta) there is a population of intermediate birds known as 'Cassiar Junco'. Although formally recognised as a subtaxon of Slate-coloured (race cismontanus), these birds almost certainly derive from hybrids or intergrades between Slate-coloured and Oregon Juncos. Whether they represent ongoing intergradation or a stable hybrid is open to question.
Anyway, whatever the reality of what Cassiar Junco actually is, intergrades between Slate-coloured and Oregon Juncos may still occur. Steve writes about this one:
"Since most consider Cassiar Junco (which breeds mostly in NE British Columbia) a "hybrid swarm" between Slate-coloured and Oregon Juncos, it is difficult, perhaps impossible to separate a "Cassiar Junco" from a Slate-coloured x Oregon intergrade that has been born outside the range of Cassiar. Indeed, the point may be academic. In any case, this birds rather chestnut back patch is somewhat atypical for what is normal considered a Cassiar."
Dark-eyed Junco intergrade ('Slate-coloured Junco' x 'Oregon Junco') (same bird as in photo ID 1244 above), Jackson State Park, Morgan County (Colorado, USA), 1st December 2012 - copyright Steve Mlodinow
(photo ID: 1245)
(See also: Oregon Junco x Pink-sided Junco, Pink-sided Junco x White-winged Junco, Pink-sided Junco x Grey-headed Junco, Grey-headed Junco x Red-backed Junco)
Dark-eyed Junco Junco hyemalis
Slate-coloured Junco' Junco hyemalis hyemalis-group
Oregon Junco' Junco hyemalis oreganus-group
Cassiar Junco' Junco hyemalis hyemalis x oreganus (known as cismontanus)