Tuesday, March 23, 2010

"Oregon" Junco

Yesterday I banded the "Oregon" form of the Dark-eyed Junco.  Note the black head, brown back, and pinkish sides.  Also note the angle formed where the sides meet the dark throat--usually forming a relatively sharp angle. Compare that angle with the rounded curve formed by the gray throat and sides of the "Slate-colored" Junco in the photograph below.
"Slate-colored Juncos" breed "across boreal n. North America south to w.-central Alberta, east to Newfoundland, and south through Appalachian Mtns. to n. Georgia."  Oregon Juncos "breed over much of w. North America, from se. Alaska south to mountains of n. Baja California and east to sw. Saskatchewan and w. Nevada; casual or accidental to East Coast and west to w. Alaska."

Years ago these birds were considered to be separate species, but, because they interbreed where their ranges meet, they were lumped together as one, now called the Dark-eyed Junco. Hence the quotes around "Slate-colored" and "Oregon." Indeed, Thomas Roberts in his 1936 classic, The Birds of Minnesota, wrote that many migrating juncos in the state are hybrids between these two juncos.

But listers beware!  Nelson et al. (see next paragraph) tantalizingly suggest "reappraisal and further study in light of prevailing views on the importance of hybridization and introgression seem likely to lead to recognition of several species in the future."

Range quotes are from: Nolan, Jr., V., E. D. Ketterson, D. A. Cristol, C. M. Rogers, E. D. Clotfelter, R. C. Titus, S. J. Schoech and E. Snajdr. 2002. Dark-eyed Junco (Junco hyemalis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/716

Finally, note the pale white wing bar in the photo of the lower junco photo.  White wing bars occasionally occur on "Slate-colored" Juncos and should not be misidentified as the "White-winged" Junco of the Black Hills.  Those birds are bigger, grayer, and even more distinctly wing barred (and not to be expected in Minnesota).

1 comment:

  1. Nice Dan, our banding crew banded what I assume was an "Oregon" junco this past November but with all that cross breeding it can be hard to tell. Photos here: http://www.twincitiesnaturalist.com/2009/10/name-that-junco.html