Dippers break the silence of the fall
A recent excursion to the Upper Rogue provided a welcome break from COVID confinement and persistently hot weather on the valley floor.
At the end of September, the relatively cool forest was already shutting down for the winter. Except for the turbulent waters, an almost disturbing silence filled the forest. There was little more than the occasional chatter from a protesting Douglas squirrel — or as many foresters like to call them, timber tigers.
There was no song. Nearly all the neotropical migrants, including warblers, tanagers and flycatchers, had departed for more benign winters in the mountains and coastal plains of western Mexico. A few juncos remained, but they kept to themselves reaping the bounty from the Douglas-firs that were shedding their seeds across the landscape. The juncos, too, will soon depart for lower elevations as the snows arrive.
Little more than the ever-present chestnut-backed chickadees and red-breasted nuthatches will remain through the winter in near silence and the endless pursuit of one more chilled spider or tiny cocoon.
It was then I heard fragments of a rich and sweet serenade from somewhere downstream. The noise of the river nearly drowned out the song. As I attempted to get closer, a small gray bird flew past heading upstream barely clearing the surface of the water. It was an American dipper.
Dippers are the only aquatic passerine or perching bird. They dive for stoneflies, mayflies and caddisflies that live among the riverbed. Worldwide there are only five species. Two occur in the mountains across Europe and Asia, two in the Andes of South America, and ours.
They are called “dippers” because they frequently bob when perched along the river. Among the river noise, it is difficult to be heard. Visual cues like bobbing and flashing their white eyelids work better. So why then do dippers bother with rich and complex songs?
It is worth the effort to closely approach a singing dipper. Their song is filled with rich flute-like notes reminiscent of a thrush coupled with the enthusiasm and endurance of a wren. Indeed, they look like a mix of both, especially with the raised wren-like tail.
Ignoring the fact that their song travels poorly in this noisy environment, why now? Why was this dipper singing in fall? The breeding season is long over. Had it lost its mate?
Over the next two days I heard three different males belting out songs struggling to be heard. It’s doubtful that all three had lost their mates. Another possible reason is to maintain the pair bond. The female may be close.
Still another possibility is the defense of territory. Dippers, unlike neotropical migrants, are unfazed by the snow-shrouded forest of winter and are residents. As long as there is open water, there is plenty of food to be found hidden in the river bottom.
Fall is an important season for dippers to advertise ownership of territory. Young birds are dispersing, looking to find and claim a section of river of their own. The longtime residents need to make it clear their section of the river is not available. I guess bobbing and batting eyes aren’t always enough.
Stewart Janes is a biology professor, emeritus, at Southern Oregon University. He can be reached at email@example.com.