Gastineau Channel

abundance of life along Juneau’s busy waterway

In late April and early May, Gastineau Channel is notable for the large aggregations of scoters. They raft up in hundreds and thousands at the mouths of Gold Creek and Sheep Creek. Most are surf scoters, whose males are distinguished by the white patches on the heads. Less common are the white-winged scoters, whose white wing patches are best seen when the wings are spread. Only careful inspection would tell if there are a few black scoters mixed in the flocks.

surf-scoters-in-the-channel-by-bob-armstrong
Surf scoters in Gastineau Channel. Photo by Bob Armstrong

Scoters are chunky, heavy-bodied sea ducks that winter along the coast. Those that winter to the south of us migrate northward in spring, often stopping to refuel in our area, toward their nesting grounds in the Interior. Canadian researchers have found a tendency for scoter migrations to follow the timing of herring spawning, which is generally later on more northerly coasts. Herring spawn is a favorite food of scoters.

On a low-tide morning in early May, a couple of friends and I walked down the beach on Douglas Island to Ready Bullion Creek. We went to see if dippers occupied their usual territory on the lower part of the creek. And yes, they were there, but they seemed to be nesting in a new site. The new place is one that for several years I thought would be ideal for them, but they had preferred to nest either down close to the intertidal or well upstream in a very narrow canyon. This time the nest site is between the former sites, on a cliff next to a nice waterfall and above a beautiful pool. (I finally got it right!)

As always, there were interesting things to be seen along the beach: two eagles with locked talons, spinning downward and breaking off just before crashing into the beach logs; a couple of migrating golden-crowned sparrows in the brush above the beach, on their way to the Interior and the subalpine habitats around here; male cottonwood trees starting to flower; a greater yellowlegs standing in the shallows; a pair of hooded mergansers flying by.

Small flocks of Barrow’s goldeneye cruised slowly along, in some cases in the company of a few pairs of harlequin ducks. The goldeneyes nest mostly in the Interior, but sometimes they nest in coastal areas—and at least occasionally in the Dredge Lake area. The harlequin females will go up along the coastal streams to nest, and (with any luck) they’ll bring flotillas of ducklings down to the sea later in summer.

The beach was covered with strange little tracks, which we deduced were those of crabs scuttling to and fro. A raven had marched in a straight line for many yards, and a deer had run down the sand. In one area, numerous holes in the sand, many of the surrounded by a tiny turret of slender, cylindrical fecal castings, may have indicated a population of some kind of worm (my ignorance is showing!).

The most interesting part of the beach was a shallow bight whose shore was densely occupied by sea stars. Many of the stars were steeply humped up over cockles or mussels (alive, alive oh!), having breakfast. They will also eat chitons, sea squirts, and limpets; the escape reaction of limpets is worth trying to see – they try to avoid the attacking star by ‘galloping’ away at Olympic speeds (relatively speaking, considering that they lack legs…). We noticed that quite a high proportion of the common five-armed star had only three or four arms, having lost the others to a predator (gulls, king crabs, other stars). Sea stars can regenerate lost arms, in time, but I wonder if there is a loss of efficiency in opening mussels or clams when there are fewer arms to pull open the shells. One sea star had a supernumerary arm, apparently regenerated from the side of a normal arm.

These sea stars displayed a remarkable array of colors—bright orange, dull orange, gray, brown with blue highlights, purple, brown with black bands across the arms, brown with dark blotches (like a rattlesnake, said a friend). It is highly unusual for any species to show such a diversity of colors. In the case of sea stars, it may be due, at least in part, to what they have been eating. And that may explain why an individual star can, reportedly, change color during its lifetime, and why a regenerating arm can be a different color that the rest of the star. A study of another species of sea star showed that diet had a big effect on the color of the star, although other factors must also be involved. I wonder if color has any effect on the risk of predation!

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