Dark-Eyed Juncos — Evolution in Action

Once I had a fancy camera that held bird images still so that I could figure out what I was looking at, I began to learn a lot more about LBJs — Little Brown Jobbies — little birds that are around us but we really don’t pay much attention to. And one of the first LBJ birds I learned about was the Dark-eyed Junco.https://amylaw.blog/2015/03/05/spring-is-coming-really/

If you look at a lot of bird books, the generic entry Dark-eyed juncos says that they are a type of sparrow with pink to orange bills and legs, and white edges on their tails; they winter south to Mexico, and breed from Alaska and southern Canada all the way to the arctic tundra. Colorado is lucky that they can live here year-round.

But reality is much more complex.

Slate-colored juncos are dark gray on their backs and heads, and white on their breasts. The line on their breasts between the gray and white forms an inverted ‘U’.

If you are from the Eastern US, the slate-colored junco is probably the dark-eyed junco you are most familiar with. They breed in Canada, and winter in the continental United States. I don’t have very good photos of the slate-colored because they usually show up at my feeders when it’s snowing. They flit in for some seeds then dart back into the trees. This behavior is typical enough that dark-eyed juncos are called the “snow bird”. Humans have co-opted the nickname to mean elderly folk who show up in warm climates in winter.

Slate-colored junco also called the “snow bird”.

As it turns out, Juncos were a tough species for me to use to start learning about LBJs. Dark-eyed Juncos come in a huge variety of subspecies — five subspecies with three subspecies having even smaller ‘races’ within them. And the most amazing thing about all this variety is that it seems to have developed just in the last 10,000-13,000 years — since the last Ice Age! https://www.audubon.org/news/dark-eyed-juncos-backyard-gems-come-dazzling-array-colors

eBird has this to say about juncos: “…incredible variation between populations. All have short pink bills and white outer tail feathers. Often in flocks in winter, foraging on the ground for seeds. Visits feeders. Subspecies include: Slate-colored (widespread), Oregon (West), Pink-sided (Rockies), Gray-headed (Rockies), Red-backed (central Arizona and New Mexico), and White-winged (Colorado in winter).” https://ebird.org/species/daejun

This is the classic Oregon dark-eyed junco — pink or yellow beak, black hood distinct from brown back or red sides, white breast, white edges of the tail. At first glance, it doesn’t look anything like the slate-colored dark-eyed junco, above. But it still has the pink beak and white-edged tail of a dark-eyed junco.

Oregon dark-eyed juncos have a distinct black hood.

The Oregon junco breeds in the Pacific Northwest, but they winter throughout the west and the Great Plains, which is why I get to see them.

Pink-sided dark-eyed junco.

This bird looks like a pale version of the Oregon junco above. Often pale versions are females while bright versions are males, but in this case, it’s just another sub-species of dark-eyed junco. The above bird is called a pink-sided junco because of the orangish-pink sides. This seems like a small difference to call out, especially when the big difference I see between it and the Oregon is that it has a pearly gray head.

But that the gray-headed junco is another dark-eyed junco. They do indeed have a gray head, so that works out. In fact, gray-headed dark-eyed juncos are all gray, except for a rusty patch on their backs, and the white edges on their tails.

Gray-headed juncos are gray pretty much everywhere except their backs, which are rusty red. Again, pink or yellow beak, white edge to the tail (you can just see that in this picture) make them a junco.

They are residents of the Rocky Mountains, and move up and down the mountain elevations more than north and south, so these are the juncos I’ll see in the mountains in the summer.

And these are just the birds that have come to our feeder! The white-winged, the red-backed, Guadeloupe — even more subspecies of dark-eyed junco are sprinkled around in Canada, the U.S. and Mexico.

WHO CARES???

Well, I do.

I care for a couple of reasons.

First, I always feel like once I can identify a bird, and know where it’s found, I know that bird a little better — it’s now a friend.

Second, it fascinates me that dark-eyed juncos are splintering into all these different forms in just 13,000 years. To give you an idea of how fast their changes are happening, dogs split off from wolves 15,000-30,000 years ago. So when these birds finally become separate species, they will be the youngest species in the world. That’s evolution in action.

And that is pretty cool.