Friday, May 30, 2014

The Dippers and the Caddisflies

By Nancy Partlow

I took my Dad to Tumwater Falls Park recently. I wanted to show him the Canada goose that was nesting in the wood pile atop the upper Deschutes falls. As I rolled him in his wheelchair to a platform overlooking the river, I glanced down and right in front of us I saw my favorite bird – Cinclus mexicanus, the American Dipper.
It was hunting from atop a log - diving quickly in and out of the swiftly flowing water behind the falls. I knew it must be feeding young, but there were no babies apparent in the immediate area. Dad and I were both amazed at how fast the bird was jumping in the river, retrieving its prey, knocking it on the log, and diving back in again. We couldn’t figure out what it was going after. They didn’t look like salmon smolts, which I had seen a dipper gathering in abundance last spring at the lower falls. What could they be?

The next morning I returned to the platform to check out the goose, which was still incubating eggs, and briefly caught sight of a Spotted Sandpiper flitting off the woodpile. Then, as I had hoped, the dipper returned to the log, this time with a baby. 

The bird resumed its activities of the previous day, but now with my zoom camera, I was finally able to figure out what its prey item was – fat, juicy caddisfly larvae. 

I was excited. I remembered learning about Deschutes River caddisfly larvae as a youngster. My brother, a fisherman, had shown me the clever little houses called “cases” that these aquatic insect grubs create out of the river-bottom materials of teeny pebbles and sand. It was one of those “isn’t nature amazing” moments that stick with you for the rest of your life. And here was the dipper eating them. There must have been hundreds of these creatures submerged beneath this small stretch of river because empty caddisfly cases littered the log’s surface. 

Fascinated, I watched as time and again the parent grabbed a larva by its head (the only part of the insect sticking out of the case) and banged the case on the log until the bug inside was knocked insensible and relaxed its grip on its only source of protection. The bird did this several times in a row until it had gathered up a mouth full of grubs, which it then unceremoniously stuffed down the gullet of the loudly-begging baby dipper.

Occasionally the caddisfly worm was so far inside the case that the dipper couldn’t grab its head. When that happened, the bird would take the whole case in its beak and knock it on the log to dislodge its tenant. 

Other times it tried unsuccessfully to poke its beak into the case to grab the recalcitrant food morsel inside.

Obviously, dippers have a well-honed search image for such underwater prey, no doubt aided by the protective shields on their eyes called nictitating membranes. Many people mistake the dippers’ striking white eyelids for these membranes, but bird authority David Sibley dispels that notion.

All of the parent bird’s feathers were worn from months of indefatigable use, but in spite of this, the dipper was singing! 

Dippers are America’s only aquatic songbirds, and this one was showing off its vocal prowess; perhaps teaching its baby how to sing, or maybe just warbling its exuberance at finding such a great food source. Whatever the reason, it was fun to hear.

Naturalist John Muir was enamored of the American Dipper, which he called the Water Ouzel, and wrote extensively about it. His description of its song is pure poetry:
The more striking strains are perfect arabesques of melody, composed of a few full, round, mellow notes, embroidered with delicate trills which fade and melt in long slender cadences. In a general way his music is that of the streams refined and spiritualized. The deep booming notes of the falls are in it, the trills of rapids, the gurgling of margin eddies, the low whispering of level reaches, and the sweet tinkle of separate drops oozing from the ends of mosses and falling into tranquil pools. 

The tranquility of the two dippers in front of me was abruptly ended when a crow landed nearby. All singing stopped, and the dipper baby, which had been bobbing incessantly, froze in place, becoming the proverbial bump on the log.
The crow, which seemed more interested in what the dippers were eating, soon moved on, at which point the baby tentatively explored the more placid waters next to the log. I enjoyed watching it learn how to become a dipper.

The next day when I returned to the park, I saw the parent dipper foraging the rapids below the upper falls, trying valiantly to keep two persistently-begging babies fed.
The parent was not nearly as successful in finding food as the previous day, and was too busy to sing. 
The water above the falls was noticeably lower and clearer, revealing a cobbled river bottom with no caddisfly cases to be seen.
Perhaps the dipper had hunted them all out. Hopefully, by next spring there will be another bumper crop of these intriguing insects to feed the next generation of dippers at Tumwater Falls Park.


All photos and videos by Nancy Partlow
(Highlighted text leads to videos.)



Dippers must be pretty tough to survive the constant battering of their dynamic environment of cold, fast-moving water. Their range extends into northern Alaska, where they are able to endure temperatures down to 20 degrees below zero. A friend recently told me that the first time he ever saw an American Dipper was in a stream at Paradise in Mt. Rainier National Park.

Here’s a photo that gives a sense of how resilient these birds are:

Here are a couple of truly gorgeous images by photographer Eugene Beckes of an American dipper with caddisfly larvae in its mouth:


1 comment:

  1. I found you via Rusty's site, and I wanted to let you know how much I enjoyed reading this post. I look forward to reading the rest of them and watching the great videos.