The American Dipper, also known as the ‘water ouzel’ or the ‘water thrush,’ inhabits high-gradient, fast-flowing river systems such as the Tuolumne River watershed. This aquatic passerine can often be observed zealously zipping up and down stream corridors, dipping into shallows to feed on aquatic insects, and nesting in protected ledges within close proximity of riverbanks.
Dippers are one of the few fish-eating birds that inhabit the Tuolumne River system; however, they mainly prey on aquatic insects such as the Orders Ephemeroptera (mayflies), Trichoptera (caddisflies), Plecoptera (stoneflies), Diptera (true flies) and Odonata (dragonflies and damselflies).
He is the mountain streams’ own darling, the humming-bird of blooming waters, loving rocky ripple- slopes and sheets of foam as a bee loves flowers, as a lark loves sunshine and meadows. Among all the mountain birds, none has cheered me so much in my lonely wanderings, — none so unfailingly. For both in winter and summer he sings, sweetly, cheerily, independent alike of sunshine and of love, requiring no other inspiration than the stream on which he dwells. While water sings, so must he, in heat or cold, calm or storm, ever attuning his voice in sure accord; low in the drought of summer and the drought of winter, but never silent.
-John Muir, Mountains of California
Generally in tributaries to the Tuolumne River, I observed several dippers, always limited to one or two at a time, feeding in the shallow stream margins. During this time, I learned about dipper processing stations. These ‘stations’ are locations where dippers bring their prey items, which are often caddisflies. After they grab caddisflies from the river’s substrate, they adeptly extract the living insect out from its carefully constructed case that is made up of particles of sediment and vegetation. I know from personal experience that this is no small task; I have had frustrating experiences with delicate forceps (tweezers), looking through a microscope, trying to do this exact same thing. So, as a result, I kept my eye out for signs of stations― caddis cases littered about boulders and bedrock along shore. On the North Fork of the Tuolumne, there is a bedrock chute covered in alluvium (fine sediments) where caddisflies can be seen making trails as a result of dragging their house around with them.
When you visit this site yourself, look out for bird nests built underneath rock ledges, the remnants of their lunch, and think fondly of this native bird. After all, dippers in this region were the favored bird of the John Muir, so it’s good to know that they have been able to persist in the face of dam regulation.
Citations:
Kingery, Hugh E (1996). American Dipper (Cinclus mexicanus), 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/bna/species/229.
Moyle, Peter. Personal communications (2009).
Muir, John. The Mountains of California. The Century Company. New York, 1894 (13) pp. 267.