All,

            The subject junco appears to lack the relatively sharp contrast
between the color on the head and the back and sides and the clearly paler
gray chin and throat as compared with the rest of the head on the Pink-sided
Junco and has some gray in the warm brownish wash on the sides and flanks.
The gray on the head also appears too dark, and as a result the dark lores,
which also are present on the Slate-colored Junco, do not appear to be as
contrasting as on the typical Pink-sided Junco. 

According to The Cornell Lab's The Birds of North America Online, a small
percentage of adult female Slate-colored Juncos (hyemalis group) are heavily
washed with brown or reddish-brown, especially on the flanks, particularly
the westernmost subspecies of this group, J. h. cismontanus, which breeds
from the Yukon to central British Columbia and Alberta, winters throughout
the West and is casual in the East and in appearance is intermediate between
the "Slate-colored Junco" and the "Oregon Junco."  Relevant excerpts from
The Birds of North America Online are set forth below. 

Finally, as noted in The Sibley Guide to Birds, some members of the
westernmost subspecies of the Slate-colored Junco approach the Pink-sided
Junco in appearance, with some females being indistinguishable in the broad
intergrade population. 

In any event, this is not a typical junco for this area and thanks to Sean
for sharing.

Gerry Hawkins

Arlington, VA

Slate-colored Junco (hyemalis group): 

Small percentage of adult females heavily washed with brown or
reddish-brown, especially on flanks. Hood usually blends with flanks and
back (i.e., no sharply contrasting boundary); dark breast and flanks meet
white of belly in smooth concave (inverted U). Some Slate-colored Juncos
(especially females and immatures) in Basic I plumage may resemble J. h.
mearnsi or other subspecies of oreganus group. Plumage of a small percentage
of J. h. hyemalis is suffused reddish brown, including pinkish buff on
flanks and brown on back. J. h. cismontanus typically are browner or buffier
on flanks and back than the others; thus, some of hyemalis group are
mistaken for oreganus - group juncos (especially J. h. mearnsi). But in
oreganus - group juncos, hood and back contrast sharply, producing clear
boundary instead of blended transition. Similarly, in oreganus group, sharp
contrast separates belly from breast and flanks; pattern of hood in oreganus
is clearly convex across breast. Hybrids and birds showing evidence of
intergradation within oreganus -group juncos are frequent; and J. h.
cismontanus is thought of as a stabilized hybrid swarm between hyemalis and
oreganus groups.

 Pink-sided Junco (J. h. mearnsi): 

 

Pearly gray head with bluish-gray cast; chin and throat paler gray than rest
of head; lores contrastingly dark to black; back and scapulars dull brown;
sides and flanks typically extensively (broadly) pinkish cinnamon.