The Bobbing Rock

You only need to sit still long enough in some attractive spot in the woods that all its inhabitants may exhibit themselves to you by turns.

~Henry David Thoreau


Campsite at Elk Knob State Park (click photos to enlarge)

In my last post I mentioned the incredible bird life at Elk Knob State Park seen in a recent backpacking trip. The gurgling stream next to camp drowned out many of the bird songs we heard along the trail as we hiked. But, after setting up camp, we were sitting and enjoying the scenery when we saw a flash of wings zipping by upstream. In a few seconds we saw the source – a Louisiana Waterthrush.

Mountain stream

Mountain stream next to camp provides excellent Louisiana Waterthrush habitat

Although referring to its close cousin, the Northern Waterthrush, a description by ornithologist E.H. Forbush is very applicable to this species as well – It is a large wood warbler disguised as a thrush and exhibiting an extreme fondness for water.  That pretty much sums it up. It is hard to believe this is a warbler. Instead of the bright spring colors of many wood warblers, the Louisiana Waterhrush is dull brown and streaky, blending in very well with the leaf litter and exposed rocks along the mountain streams they call home. And unlike the warbler neck pains you typically get from staring up in treetops trying to identify most spring warblers from below, you can sit quietly and watch this species walking on the ground and hopping from rock to rock as it forages along a babbling brook.

Since I rarely carry telephoto lenses while backpacking, I can’t show you close up images of this bird, so I refer you to the Cornell Laboratory of Ornithology website for some basic information on Louisiana Waterthrushes and how to distinguish them from Northern Waterthrushes. What I can tell you is these birds are fascinating to watch. One of the distinctive behaviors of waterthrushes is their tail bobbing as they walk. A few other species do this, most notably some other birds frequenting the shores of waterways – Spotted Sandpipers and American Dippers. I have yet to find a really good explanation for this behavior. Quite honestly, if these birds did not constantly bob as they walk, it would be much more difficult to spot them along the rocky stream banks. I hope there is some benefit to the bird for this bizarre behavior, because it seems to me it makes them much more susceptible to potential predation.

After watching the first bird for a couple of minutes, it became clear that there was probably a nest nearby. The waterthrush was gathering food, lots of food, in the form of various insects along the stream, and then started bobbing its way toward us. As we watched, it bobbed on a rock right across the creek from our tent, then flow up under the overhanging bank and disappeared – a nest! In a few seconds, it dropped down next to the creek, and quickly walked off downstream. We sat and watched this routine for several minutes. The adult birds came to the nest every 5 to 10 minutes with a beak full of bugs, bobbed on some rocks below the nest, and then flew up to feed the young. In between one of the feedings, we hopped across the stream to take a closer look.

Nest site

Nest site under overhanging stream bank

The nest was tucked up under an overhang, surrounded by some dangling tree roots. It is along the inside of the upper left side of the “X” formed by the gray roots in this photo…see it? Look a little above the center of the photo, just to the right of the left branch of the X.

Louisiana Waterthrush nestlings

Louisiana Waterthrush nestlings

Here it is up close. We didn’t want to disturb the birds, so we took a quick picture or two and then retreated back to the other side of the creek. We watched the adults as they continued to bring what looked like super-sized meals to their tiny babies. But, notice how big the beaks of the young are…I guess they can handle the large prey being brought to the nest by their busy parents. Although it was difficult to identify a lot of the food items through binoculars (especially since the adults are constantly bobbing up and down ad side to side), we did see the what looked like damselflies, dragonflies, mayflies, stoneflies, cranefly larvae, and many other large insects filling the beaks of the adults.

You can imagine how I was wishing for a telephoto lens to capture some images of these busy adult birds and all that food in their beaks. I did have my 17-40mm wide angle. So, I decided to try something. The adults did not seem bothered by our presence and continued to feed their young even when we were moving about camp, so I walked across the stream when they had gone out to forage and set up my camera to do some remote video.

Nest site and camera

Nest site and camera

The birds seemed to always stop in one general location and bob repeatedly before jumping up to the nest. I set the camera on some rocks, covered it with my green raincoat, and then laid some more rocks and leaves on top to help it blend a little better with the irregular patterns along the stream bank. The adults didn’t even seem to notice after their initial visit back to the nest. It took several takes, but I finally captured a couple of clips to share.

This is a typical sequence where an adult bird comes up to the main “bobbing rock” for a few seconds and then steps away.

A few seconds later, the adult comes back, begins to bob vigorously while looking up toward the nest, and then suddenly flies up to feed. The usual routine was to then drop back down and scurry off a few feet before flying away to forage some more. We did see one adult pause for several minutes and take a splash bath in the water and then preen.

Fecal sac dropped in stream

Fecal sac dropped in stream

Every three of four feeding trips ended with an adult bird bringing out a fecal sac produced by one of the young birds. In most species I have observed, adult birds fly off with the fecal sac and drop it many yards from the nest. This makes sense in terms of reducing the chances that potential predators can cue in on a nest location from the droppings of the nestlings. But these adults always carried the fecal sac to the edge of the stream and dropped it in the water, where it was usually quickly carried off downstream.

Watching the feeding activities of this pair of adult birds was amazing. It isn’t often you are in a situation to observe this sort of behavior for an extended period of time. As we broke camp on the second morning, I watched them bring a beak full of wings and abdomens one last time, dance on the bobbing rock, and disappear into the nest. I wished them well and thanked them for a rare glimpse into the private life of a special species that some have called, the “feathered trout”.

4 thoughts on “The Bobbing Rock

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