Some special events in Juneau natural history

Low tides expose seldom-seen creatures; bays offer hordes of fish

Posted: Sunday, December 18, 2005

Surrounded as we are by a variety of habitats and wildlife, it is easy for a curious naturalist to get distracted. There are, however, some special events in our local natural history that warrant particular attention.

Some of these are relatively well-known to local observers, while others seem not to have attracted much notice. Here are a few of these special events.

Extremely low tides expose organisms we seldom get to see close-up. One can find sea stars (including the sunflower star), sea urchins, hermit crabs living in their borrowed shells, large anemones, beautiful marine slugs (nudibranchs), several species of chiton, sturdy snails known as whelks (sometimes with their egg masses), sea cucumbers and marine worms.

Peek under a few rocks and discover small octopi, baby king crabs and sponges. A good place for this is the sand bar that connects Shaman Island to the north Douglas Island shore, accessible by the Outer Point trail.

In some bays in spring, there are hordes of pink salmon fry, less than 2 inches long, moving along the shore close to land, where they are quite safe from other fishes but vulnerable to hungry birds. In tiny tide pools, you might uncover some long, thin, very funky fishes, perhaps some crescent gunnels (with light spots on their backs), which prefer vegetative cover in the subtidal zone but sometimes get trapped by the outgoing tide. More likely to be found are high-cockscomb pricklebacks, whose elongate body is almost all muscle, because all the internal organs of digestion and reproduction are crowded up right behind the head. The reasons for this peculiar arrangement are not clear. Pricklebacks get eaten by ducks and herons, as well as sculpin and salmon.

In addition to the spring and fall shorebird migration on the wetlands (mentioned in a previous article), there's the fall migration of hawks over the mountain ridges. Several species of hawk move south, helped by the updrafts created by the ridges, so the best time of day is from late morning onward, when the air has warmed and started to rise.

Two great places to watch this are up on Gold Ridge, accessible by the Mount Roberts trail and the tram, and Thunder Mountain, reached by the trail of that name. If you sit comfortably beside a rock up there, you could see a Northern Harrier or an American Kestrel (a small falcon) cruising the meadows for small birds or mice, or a sharp-shinned hawk searching the brush for birds. There may also be other kinds of falcon, red-tailed hawks, rough-legged hawks from the northern tundra, a few golden eagles and occasionally other species. And while you're up there, don't miss the ravens cavorting in pairs and trios. In August, there might be an additional bonus if the white flowers of the Sitka Valerian are open - they attract clouds of Milbert's tortoiseshell, a lovely butterfly that has dark wings with a golden-orange border. Supposedly, cats and rats love valerian, and the legendary Pied Piper of Hamlin might have carried it in his pocket to lure the rats from that town.

Go out the Road, and several events are on offer in the right season. Near the shrine, off Crow Point south of the mouth of Eagle River, and between Benjamin Island and the mainland, wintering humpback whales cruise back and forth, often tended by opportunistic Steller sea lions that snarf up herring that flee the jaws of the whales.

In spring, what's left of the Lynn Canal herring stock spawns on rocky shores at various points between Berners Bay and Bridget Cove. For a few days, this spawning aggregation attracts hundreds of eagles that swoop down from the spruces to snag adult herring, and squabbling gulls crowd the intertidal zone to feed on herring eggs. Whales and sea lions come too, and the chunky sea ducks called scoters form chains of foragers diving after subtidal eggs. Watch what happens when the sea lions come too close to the scoters! Freak out!!

Even non-naturalists can spend hours watching this show.

Fellow naturalist Bob Armstrong, marine biologists Mandy Lindeberg, Adam Moles, Sherry Tamone and Bruce Wing, and hawk-watcher Gus Van Vliet contributed to this brief account of special events that are worth seeking out. But any observant person can probably find other local natural events that excite the curiosity and tease the imagination.

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

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