May outing finds dippers near Fish Creek

Posted: Friday, May 21, 2010

On the only crummy day in a week of pleasant May weather, Parks and Rec hikers headed up the Perseverance Trail. The winter's rockfalls had been cleared away, but the guard rails had yet to be replaced. The trail was mostly dry and easy, although there was still considerable snow near the end. The bridge across Lurvey Creek is still broken but passable by the sure-footed.

Photo By Bob Armstrong
Photo By Bob Armstrong

Avalanche damage of winters past is very evident near trail's end. Bedraggled cottonwoods seem to have lost even more branches to strong winds, but they stubbornly put out leaves on the few remaining limbs. Alders and willows lie askew--dead, dying, or struggling to crank out a few new shoots.

Among the more arcane topics of conversation was a discussion of how to distinguish male and female willow catkins (the so-called pussy-willows), which grow on separate trees. Sitka alders had profuse crops of male catkins, and on the same plants we could just discern the tiny new female cones that will develop into the more familiar hard, brown cones-some of which remained on the plant from last year.

We didn't linger long-a cold wind drove the rain in our faces until we turned to go back down. But the fox sparrows were singing their territorial songs, robins and hermit thrushes sang and scolded. Townsend's warblers sang, too; one of my former field techs rendered their song as "I want my ju-ju-beeeeeees!" Ruby-crowned kinglets cheerily sang out "Here, here, here, look at me, look at me, look at me!"

The next day was nicer, and I went with two friends to check out a section of Fish Creek, where we hoped to find a nesting pair of American Dippers. We made a bushwhacking shortcut over to the official trail near the part of the creek we wanted to explore. The trail itself is sorely in need of some work; long stretches consist largely of slimy roots and mudholes.

At our first stop, where I'd previously seen a pair of dippers foraging, we found nothing. Yawn! To reach the second stop, we dropped down off the trail, around a huge wind-thrown tree, and down some more through a snarl of devil's club. Soon after we settled in the brush on the streambank, a dipper suddenly appeared, as if by magic.

It hadn't come along the stream, so it must have come from the nearby cliff-and that probably meant a nest was there. From our viewpoint, the cliff was screened by a pair of fallen trees, so we waited until the bird came back and flew in, confirming that she had a nest there. By squirming around and nearly lying flat on the bank to peer through the treefalls, we could just see a nice nest packed into a crevice on the cliff. The bird stayed in the nest, so incubation was underway.

Not too far upstream, another pair is resident. At this site a few years ago, we witnessed an event that has been observed occasionally in several songbird species but is really rare: a hostile takeover of a female by a new male. The newcomer drove off her mate, destroyed her brood of little chicks, and induced her to start a new nest with him.

Such behavior is well known in lions and bears (among others), in which a male may kill a female's cubs, so she comes into heat again, and then is ready to mate with the new male. As reprehensible as this may seem in human terms, it seems to work as a reproductive strategy in numerous species. The infanticidal males increase their reproductive output (unless, of course, they happened to be the father of the dead cubs, which sometimes could be the case in bears). The bereft females replace their losses as soon as possible, and their sons may inherit the tendency to follow this strategy.

Mary F. Willson is a retired professor of ecology.

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