Around the world, there are clay-colored thrushes, island thrushes, creamy-bellied thrushes, rufous-backed robins, bare-eyed thrushes, Siberian thrushes and common (Eurasian) blackbirds. These and more all are closely related to our American robin.
Apparently robins are on to something. They have been spectacularly successful.
I don't think anyone living in the Rogue Valley this winter would disagree. We have been invaded by a hundred thousand robins or more. It started about mid-October with the ripening of a bountiful crop of madrone berries. The valley colored up with both berries and the robins and waxwings that followed. At times, a given hillside would come alive with a cacophony of sounds, including a variety of calls and fragments of song as they swarmed over the madrones. New birds arrived. Others departed. Given the numbers, air traffic control would have been helpful. After a couple of days and the berries depleted, they quickly find other hillsides to mob.
Each day as shadows begin to lengthen across the valley, they lift off in numbers. Robins do not fly in tight flocks as do waxwings or starlings. Instead, they fly high and widely spaced. A great many head to the large roost along the Rogue River where 50,000 and more gather nightly. A second smaller roost has formed along Bear Creek just south of Medford. I'm sure there are others scattered about the valley.
If you missed the show in the foothills and at the roosts, you now have a second chance. They are now carpeting pastures and lawns. With the madrone berry crop having been harvested, they change their feeding behavior, trading sweets for meat. It is now worms and other invertebrates that feed the horde.
Where do they all come from? Some I suspect are local birds, but others come from across Oregon. At Crater Lake in the summer, you will find robins around the edges of the mountain meadows at timberline. You will find them in open forests, backyards and the high desert, too. As I said earlier, robins are quite successful.
Many come from even farther away. Not only are they found in diverse habitats in Oregon, their range in the west extends north all the way to Nome and the Yukon.
Take a careful look at the individuals in your yard. Some are quite pale; others dark. Some have bright white corners to their tail; other not. Some have a bold striped throat; others faded. These subtle differences betray their diverse origins. In winters such as this, the flocks are a mix of birds from all over.
In fall, they seek the best foraging opportunities to sustain them through the winter. In some years, many pause only briefly in the Rogue Valley. On they go into Northern California, perhaps to the foothills of the Sierra Nevada or the Klamath River canyon, gathering wherever dining is best. In other years, the large flocks may not make it this far south if points north provide abundant fare. This winter, our backyard is the place to be because of the heavy madrone berry crop.
Sometime in February, we will lose our guests with the approach of spring. What about next year? It's anyone's guess. But keep your eyes on the madrones.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.