Lots of natural history going on in wetlands

A stroll through the area presents the traveler with a wealth of wildlife that call the place home

Posted: Sunday, December 04, 2005

The premier access to Juneau's wetlands is the dike trail near the airport, but another good route is the lower Fish Creek trail out to the mouth of the creek, starting near the bridge on the North Douglas Highway. There is so much interesting natural history going on out there that it is hard to know where to start the telling.

But let's start with the sloughs on the "outboard" side of the dike trail. These are nursery areas for some marine fishes, as well as habitat for worms, clams and tube-building amphipods (shrimp-like crustaceans). All this potential food brings in the predators. For shorebirds, the peak of activity is in late April and May for the northward migration, and July-August for the southbound birds. The wetlands are an important area for these birds to "refuel" during their long-distance travels, so they should not be disturbed. You might see greater yellowlegs snatching up small sculpins with their skinny bills or dowitchers, with their preposterously long bills, probing the sediments for crustaceans, worms, and clams. If you see a litter of tiny pink clam shells lying on the mud, it might indicate an intriguing chain of interaction: Clams have a tube-like siphon used for breathing and feeding, and a buried clam can send its siphon up to the surface. But there the hungry little flatfish (starry flounder, two species of sole) often nibble off the end of the siphon. This forces the clams to come up closer to the surface, where they are then more vulnerable to foraging shorebirds. In some areas, the sediment is simply paved with little pink shells, suggesting intense foraging activity.

The sloughs and the deeper ponds on the "inboard" side of the dike trail host waterfowl, including several kinds of ducks, Canada geese, and even the occasional swan. White-fronted geese graze on grasses near the ponds. On your lucky day, you might see a family of river otters humping along the mudflats or cavorting along the sides of the ponds. The resident pair of bald eagles nests every year in the trees near the ponds, but their nesting success is variable.

If you take the unofficial trail out along the Mendenhall River across the mudflats toward Fritz Cove, you could encounter (in season) hordes of little sandpipers scurrying after insects and crustaceans. In certain very sandy areas, the slender sand lance (or needlefish) sometimes lie buried in the wet sand. A favorite prey of many birds in open water, sand lance aren't safe even hidden in the sand. Crows and ravens come and dig them up with high success (how do the birds know where the fish are?), and eagles "dance" on the sands to force the hiders to the surface. Gulls occasionally dig or "dance" for themselves, but more commonly hang out near the eagles and crows to steal their prey.

The grass and sedge zone seethes with migrating pipits, longspurs, and savanna sparrows in spring. They are hunted by day-flying short-eared owls and harriers. When there is a super-high tide, the voles (chunky small mammals) that invaded this zone have to swim for their lives, but sometimes get nabbed by opportunistic, predatory ravens, eagles, and owls.

Winter on the wetlands is not an empty time. Besides the several species of duck, the resident variety of Canada goose can be seen grazing on sedges, always with one sentinel bird standing upright and alert. In hunting season, however, the wise geese and ducks often move to Auke Lake during the day; there is little there to forage on, so these birds return to the wetlands at night to feed. Perhaps you'd find a troop of gulls and crows, and even wintering magpies from the Interior, poking around in brown fronds of rockweed for the rich supply of snails and amphipods. And there's a little flock of rock sandpipers and dunlin that usually hangs out near the mouth of Salmon Creek.

Although much of the action occurs on the flats or in the shallow water, the terrestrial habitats along the edges of the wetland are pretty lively at times. The crow colonies near Fritz Cove are noisy, busy places in spring, when the adults bring food to their blue-eyed chicks. Migrant flocks of sparrows and thrushes throng the underbrush, with an occasional merlin lurking in the trees in hopes of catching one unawares. Song sparrows nest at the forest fringe, and killdeer nest above the high tide line. Early in spring, the migratory ruby-crowned kinglets practice their rollicking, wonderful songs before moving on to find their territories for the year, but a few stay to nest in the conifers near the trails.

I've only scratched the surface of the richness of natural history out on the wetlands. Lots more of interest awaits the curious and observant walker on these trails.

• Mary F. Willson is a retired ecology professor and a Trail Mix board member.

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