Juncos are the first birds I see on these cold mornings. The dark heads and chests of this slate-colored form of Dark-eyed Junco are black spots against the white of this new snow.
Just a few days ago, I was taking photos of the western subspecies of this fellow, in sunny California, the Oregon Junco. What a difference a few days (and a few miles) makes.
Same dark eye, same pinkish bill, but the Oregon Junco has browner sides and back in place of the slate gray color of the our eastern and midwestern race. The gray in the Oregon Junco is confined to a hood over its head, rather than an over-all background color. That is, the two forms of Junco are quite morphologically distinct.
As noted before in an earlier post, Dark-eyed Juncos (Junco hyemalis) are actually a diverse collection of six subspecies. What I didn’t know when I wrote that post is that Juncos are a very rapidly evolving group, with each of the subspecies occupying a slightly different geographic range and migratory pattern so there is little contact between them — the perfect conditions for evolution of new species.
And…this has all happened in just the last 10,000 years since the last glacial retreat, as Yellow-eyed Juncos moved northward from Mexico to invade new territory in northern North America. The subsequent local evolutionary changes due to mutations and geographic separation have resulted in a distribution of subspecies that looks like the map below. This diversification is one of the fastest rates recorded for vertebrates. Evolution in action!
JU stands for Junco in the map below. The different types are SC (slate-colored), WW (white-winged), OR (Oregon), PS (pink-sided), GH (gray-headed), and RB (red-backed). YEJU is the ancestor of all of these — the Yellow-eyed Junco of Mexico and Central America.