Mary Willson On the Trails

Peterson Creek is an easy portal to view wildlife

Posted: Sunday, May 07, 2006

From the end of the North Douglas Highway, this flat and easy trail goes under a new power line to the creek and follows the creek upstream for about a mile.

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It then crosses the stream on a fallen log and continues upstream before sneaking over to the beach on the west side of the island (it is easy to miss this turn!). The trail goes right past an enormous rootwad belonging to a tree that lost its fight with the wind. It is easy to observe the shallow root system and be reminded of just how little soil is available in most places around here for the extension of tree roots.

Peterson Creek is a rich stream, with lots of aquatic invertebrates. Although American dippers don't nest on this stream, several of them may spend the winter here, foraging through holes in the ice or on the delta. Thousands of chum and pink salmon spawn here, as well as numerous coho salmon, and the stream is an important rearing area for young coho. This creek is one of the top two salmon streams on Douglas Island, in part because so much of it is relatively flat and easily accessible to incoming fish.

The black bears on the island visit this stream often when the salmon are running; bear-chewed salmon carcasses litter the banks and are dragged back into the forest. These carcasses and the digested fish remains in bear scats provide nutrients for trees and other plants; the effect of such sea-run fertilizer can be measured in the leaves and in the rate of tree growth. Enriched leaves may support more insects and could account for our observation that the density of nesting songbirds tends to be higher along salmon streams than along streams without salmon.

As the trail leaves the power line and enters the forest, there's a fine springtime garden of western skunk cabbage. Sitka black-tailed deer love to nibble the yellow hood and inner flowering spike, leaving mutilated stubs behind. Unlike its eastern cousin, this skunk cabbage does not generate heat to attract basking (and pollinating) flies; instead, it is visited by hordes of tiny brown beetles. They hide in the furls of the yellow hood when the weather is nasty, but crawl all over the spike of flowers on decent days, eating and carrying pollen. This is a rendezvous site for males and females, and you can often see them crawling about in pairs, all covered with pollen. The flowers on the spiky inflorescence are female first, and after several days as females, the pollen sacs open and the flowers are male.

The beetles are most commonly found on inflorescences during the male phase, but when conditions are just right (maybe the females send out an alluring aroma?), they congregate on female-phase flowers, having carried pollen from male to female and thus pollinating the flowers. Occasionally, the hoods are green instead of bright yellow, but the beetles visit the green-hooded inflorescences much less than the yellow ones.

This general area is where I once found the only brown creeper nest I ever discovered, secreted behind a flap of loose bark on a young hemlock tree. The little cryptic bird inhabits stands of large, old-growth trees and scuttles up tree trunks, picking up insects. My field crew encountered several red-breasted sapsucker pairs nesting surprisingly close together. We don't normally think of these cavity-nesters as colonial, so perhaps there just happened to be an unusual concentration of the right resources here. Sapsuckers are highly specialized woodpeckers that find much of their food by drilling rows of small holes in the bark of alders and other trees, and foraging both on the sap that wells up in the holes and on insects attracted to the sap.

The beach on the west side is a great place for a picnic on a sunny day (make your fire below the high tide line!). Sometimes humpback whales or a few Steller sea lions cruise by. A seal or two usually inspects any group of people on the beach. An armada of chunky scoters might perform their amazing diving chains - a column of hundreds all dive in sequence at the same spot, and all surface in sequence at another spot, like a long conveyor belt of ducks. Apparently no one knows the function of this behavior.

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

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