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The richness of Sheep Creek Valley

Posted: November 25, 2011 - 1:01am
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A frozen but still beautiful jelly fungus, probably the one called witches' butter.  Bob Armstrong
Bob Armstrong
A frozen but still beautiful jelly fungus, probably the one called witches' butter.

I go up into Sheep Creek Valley several times a year; it’s one of my favorite places in Juneau. I was there in mid-November with Juneau Parks and Recreation hikers, and we spotted several things of interest. It had snowed recently, so tracking was good. We found tracks of squirrel, deer, mountain goat, a possible weasel, a large canid that could have been a wolf or just a big dog, and lots of porcupine tracks. Two porcupines scuttled off into the brush as we walked by.

A big conifer tree had a large squirrel midden around its base; discarded cone scales and cores covered many square yards. The main cache of full cones was underground, but this red squirrel was not content with that — it had also wedged cones into every available space between the roots and in grooves of the trunk.

We found a beautiful orange and yellow fungus growing on a dead branch. It is a type of jelly fungus, possibly the one called “witches’ butter.”

Some of the more enterprising hikers went up the slope at the back of the valley, far enough that they were wading in thigh-deep snow. Others, less energetic perhaps, were content to perch streamside for a relaxed lunch break. The creek was running crystal clear and wide open, so we had hopes that a dipper might show up. Indeed, one did, prospecting for aquatic insects along the edge of the water and moving quickly upstream.

Sheep Creek Valley is among the first places I worked when I came to Juneau more than 20 years ago. My first big project was to census nesting birds in various habitats; there seemed to be no previous studies of breeding bird communities that would provide an estimate of avian diversity and abundance in different habitats around here — very basic information for future ecological studies.

So for several years, in spring and summer, my field techs and I studied bird communities in Sheep Creek Valley and elsewhere in Juneau. We counted birds, using a standard protocol, by sight and by songs and calls. We found that this valley has a very rich community of nesting birds, arguably the richest one in our area. For example, we counted several kinds of warblers, sparrows, and thrushes — more kinds than in the spruce-hemlock forest.

Along with the standard censuses by sight and sound, we regularly mist-netted birds in the understory. Our black nylon nests were 12 meters long, and we would set up an array of about 10 nets in various places. Then we’d walk the array of nets every hour or so, extract and weigh the birds, and release them. Among other things, the net captures helped us detect birds that were quiet and secretive.

There were a few bears in the valley. Occasionally, we would glance up as we extracted a bird from a net and see a calm bear sitting near the end of the net and observing all of our actions! They didn’t seem to have designs on us or on the birds; apparently they were simply curious.

Our other main activity was nest-searching. This is hard work and lots of fun, rather like a continual treasure hunt. By following a bird for a while, often on several occasions, eventually one deduces the approximate nest location, and then careful searching reveals a nest. It often takes several hours of detective work, perhaps over several days, to locate a nest this way. Once a nest was found, we monitored its progress, from incubation of eggs to care of nestlings to fledging — or until the nest failed. Then, for each species, we could calculate the percentage of nests that successfully produced young. For example, about 65 percent of yellow warbler nests were successful, but only about 30 percent of robin nests and roughly 25 percent of fox sparrow nests were successful.

A principal cause of nest failure was predation on eggs or chicks. By installing small cameras that were triggered by removal of an egg, for instance, we learned that predators include Steller’s jays, red squirrels, mice, and even shrews (see accompanying photo). But Sheep Creek had fewer egg and chick predators than conifer forest.

All of that work required us to begin at dawn, because bird activity is generally greatest early in the morning. The days are wonderfully long in spring and summer, so that meant we started work by 3:30 a.m. or so (and had to get up around 2 a.m., to get to the study sites; this was not so wonderful!). Nevertheless, I look back on those days with much pleasure (perhaps especially because I no longer have to crawl out of bed at crazy hours).

• Mary F. Willson is a retired professor of ecology.

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