Sheep Creek Valley

nest-building, a song chorus, and a wildflower show

In early June, Parks & Rec hikers went up the Sheep Creek trail on a day of fitful rain showers and intermittent sunshine. This is a favorite trail, but it was clear that the trail could use some work! The uphill portion of the trail is seriously eroded by water coursing down the trail. The long traverse below the road is cut by deep erosional gullies and the edge of the trail is collapsing in spots. Along this stretch, cow parsnip overhangs and obscures the trail. Once in the valley proper, the going is easier, although several wind-shattered cottonwoods and sagging willows lie across the trail and there are more erosion cuts. Some of these things are easily fixed, while others are significantly more challenging.

This was a good time to go up into the valley, because it is rich in nesting, singing songbirds. Even though the P&R summer hikes begin well after the early-morning chorus of bird song (and my hearing is not as good as it once was), I identified the songs of twelve songbird species, plus hooters on the hillsides. One species, in particular, was a treat: Swainson’s thrushes commonly nest up there but they arrive later than the others; I don’t usually hear them until June. By that time, robins and fox sparrows are feeding chicks and juncos have fledglings.

swainson's-thrush-by-bob-armstrong
Swainson’s thrush with nest material. Photo by Bob Armstrong

Swainson’s thrushes nest all across northern North America and down along the Rockies. They spend the winter mostly in southern Central America and northern South America, although some go as far as northern Argentina. When they at last arrive here in spring, the female builds a nest, usually in the understory, lays her eggs and incubates them, while the male sings. But both parents tend the chicks. Hearing the song of that species is certainly a treat for me, but my favorite remains the ruby-crowned kinglet’s cheering carols from the canopy.

Right next to the trail we found a very large scat of a carnivore, full of fur and bones, artistically arranged. A wolf (or possibly a bear) had dined well, probably on marmot.

On this hike, some of the wild flowers were appearing—lots of buttercups, some chocolate lilies and miner’s lettuce, three kinds of violets, a few enchanter’s nightshade. Occasional salmonberry canes bore flowers, but there were wide stands of dead canes, some of which showed no evidence (?yet) of new canes coming up at the bases of the old ones. Does that bode ill for salmonberry production up here this year?

A special floral sighting was a clump of some kind of saxifrage, growing on boulder. We’d seen this on previous hikes too and noted the leaves with three sharp terminal teeth. That made identification simple—the three-toothed saxifrage. The leaf margins have scattered hairs, a feature that led us astray for a while, but consultation with real botanists eliminated the confusion and confirmed the name. This species is not common in our area, but it seems to be the only saxifrage here with three-toothed leaves. The white petals have reddish spots on them (so does another species, but that one has different leaves). It’s fun to try to figure out such things and learn new species; now if I can just remember all the distinguishing features…

Of course, having the right name is just a small part of any story! Many questions lie in wait for curious naturalists. What insects pollinate this plant? What is the function of the spots on the petals? Do the marginal hairs on the leaf deter some herbivores? Does this plant typically grow on rocks? And so on. That’s where the real interest and fun lie!

Just for fun of a different sort, on a completely different topic: I put up a peanut butter feeder on my deck this spring. A simple thing, it consists of a small block of wood with pits (for peanut butter) drilled into both sides of it. This dangles on a hook where I can see it easily, while lazing in my big comfortable chair. The chickadees found it almost immediately and visit it regularly. Did they know that this funny-looking thing might have food or are they just curious? Once there, one experimental peck would tell them there were goodies to be had, worth coming back for. For several weeks, I saw only chickadees there. Then the juncos began to come. Maybe they saw that the chickadees were making repeat visits and decided to check it out. They are considerably larger and much less acrobatic than chickadees, but they somewhat clumsily began to perch on top and reach down to the peanut-butter-laden holes. As time went on, they became more adept and more skillful at extracting several nice bites before losing their balance and fluttering down. Clearly they were learning how to exploit a new resource!

Occasionally other birds came too; a hairy woodpecker clung to the side of the feeder and reached quite easily over to the food source. A Steller’s jay sat on the deck railing, scoped out the situation, and flew straight at one of the gobs of peanut butter, snatching out a good mouthful on its way back to the railing. That worked, so it repeated the maneuver a couple of times. But it has not been seen again.

 

Some June sightings

a panoply of early-summer observations

The Sheep Creek trail in spring and early summer is almost always good for hearing bird songs, but this day was hot (in Juneau, that means over 70 degrees F) and we were there late in the morning, well after the usual dawn chorus. So I was a bit surprised that the listening was still quite good. I heard several Swainson’s thrushes, which arrive from their wintering area well after the other songbirds. Fox sparrows and robins were singing, presumably starting second broods. A few kinds of warblers were sounding off here and there, and even ruby-crowned kinglets, who start their lively concerts in late March, still sang a little (albeit a trifle feebly).

We found two treats from the plant world. One was a healthy specimen of three-toothed saxifrage (Saxifraga tricuspidata) on a rock near the trail. This species is not common here, being mostly a species of the Interior. It has spotted petals, as does the related spotted saxifrage, which has small, rounded leaves (no teeth).

The other good find was a happy little stand of a parasitic plant called (among other names) pinesap. The taxonomy of this plant has changed, reflecting great confusion about its relationships. It might be called Monotropa hypopitys or Hypopitys monotropa; related to the wintergreens, it is now categorized in the blueberry family (Ericaceae). In any case, the plant is less confused than the taxonomists: it has no green tissue and is entirely dependent on its hosts for nutrition. Mycorrhizal fungi connect the parasite to conifer trees and transfer nutrients to the parasite. The flowers of pinesap are pendant until pollinated (self-pollinated or perhaps by bees?) but become erect when mature and ready to disperse seeds. These plants are reported to be yellowish if they flower in spring or summer, but reddish if they flower in fall. I have not seen this plant very often around here, but we did see another one this year, over on west Douglas.

June-29-Pinesap-1-kerry
Photo by Kerry Howard

A small excitement was stirred by a wasp nest adjacent to the trail, on the ground. We could see the paper wall of the nest through the torn vegetation. Something had already disturbed the colony, which was swarming over the trail as we went into the valley, and the swarm of unhappy wasps was still there two hours later, when we left. No casualties to passing humans, but that nest may not survive.

Gold Ridge never disappoints us: if we tire of looking for marmots or watching eagles catch the thermals to soar up the face of the ridge, there are some nice plants to inspect. I found a pair of frog orchids along the trail in mid-June, but by late June they were gone—simply finished or maybe trampled. More could be found by a good observer somewhat higher on the ridge. Butterworts, which catch insects on the sticky leaves, had flowered in the early part of June and by late June some of them were setting seed. The inky or glaucous gentian, with its unusual blue-green flowers was ready to bloom in late June.

Earlier in the season, we had thirty seconds of intense excitement: from over our shoulders came a prolonged, piercing scream and a dark falcon in hot pursuit of a songbird. The songbird dove into a thicket below us. The merlin circled ‘round and back up the ridge, hoping for better luck.

Near the glacier in late June, the dippers had raised one early brood of chicks, but sadly, showed no signs of raising a second brood, even though the pairs that nest at this site often do so, and there was plenty of time this year. Porcupines were busily shredding cottonwood leaves. The sockeye were not yet in and the bears were making themselves quite scarce. A few years ago, during several spring seasons, bears were commonly seen up in the cottonwood trees, feeding on the catkins and leaving lots of broken branches, but we have not seen much of that activity in recent springs. Quite puzzling!

We had fun keeping track of the robin that chose to nest under the raised walkway. How she tolerated the thousands of tramping feet overhead is a mystery. But she incubated four eggs; one hatched a day after the others, indicating that incubation had begun with the third egg. The female sat on her eggs for around twelve days. When they hatched, the male appeared, and both parents tended the chicks. In early July, the nestlings survived the rising waters of the jökulhlaup by a few inches and fledged after about two weeks in the nest.

Sheep Creek Valley

trailside discoveries and memories of field work

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 Parks and Rec 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. Other, less energetic perhaps, were content to perch at 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 over twenty 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 twelve meters long, and we would set up an array of about ten 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 sixty-five percent of yellow warbler nests were successful but only about thirty percent of robin nests and roughly twenty-five 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 three-thirty or so (and had to get up around two 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).