Early May on North Douglas

a spring meander and some rare sightings

With two treasured companions, I set off on an easy stroll on the Rainforest Trail on North Douglas. As usual, we went in search of nothing in particular and whatever things of interest we could find. Not having a specific, predetermined goal is often a good way to stumble upon the unexpected or just touch base with the familiar.

At the trail head, we meet a couple of Fish and Game biologists who were monitoring bat movements. They shared their discovery of a marked bat that was apparently roosting in the cliffs next to the beach. This little brown bat, a female, had been tagged at Fish Creek. The biologists reported that other marked bats were also moving around to different places in Juneau.

On down the trail, we encountered a small flock of ruby-crowned kinglets that included a brown creeper. The creeper hitched its way up a big dead tree and spent at least a minute checking out the space behind a loose flap of bark—just the kind of place creepers like to put their nests.

brown-creeper-photo-by-bob-armstrong
Brown creeper. Photo by Bob Armstrong

Down on the beach, we found deep windrows of rockweed piled up way into the beach-rye zone, clear evidence of recent high tides and high winds. Now the tide was low, and we ambled along the water’s edge, peering into rocky crevices and turning over rocks (and turning them back, too!). Some rocks were obviously favored habitat, housing quite a community of miniature critters: dainty six-armed sea stars only half an inch across, tiny limpets and chitons just two or three millimeters in size, sea cucumbers an inch long or less, and an occasional miniscule sea urchin. Toothpick-size towers stuck up from the mudflats; excavation revealed skinny tubes of sand grains, presumably inhabited by some kind of worm.

I was fascinated by the burrowing anemones, buried up to their tentacles in muck. They came in many colors, including green, tan, yellow-orange, and brownish, all with white bands on the tentacles. They may come in many other colors as well, including red, blue, and black, depending on location. Many of them had bits of shell stuck around their bodies, so when they retracted, all one saw was a ring of broken shell about the size of a silver dollar. They are reported to feed on fish eggs and small, floating invertebrates.

We perched on Shaman Island for a while, just to watch what might be going on in the coves on either side of the tombolo (a.k.a. the spit) that connects the island to mainland when the tide is out. A group of twenty or thirty black-bellied plovers prospected over the sand flats (and I got a quick reminder-lesson on how to tell them from other plovers that have black fronts). Crows were foraging in the mussel beds, sometimes walking around with straggling bits dangling from their bills and seeming to cache their prizes among the cobbles. Groups of harlequin ducks and common goldeneyes floated peacefully around the edges of the covers.

A sizable flock of scoters suddenly erupted in panicked flight and fled out around the point. Just the sort of thing they would do if an eagle swooped down over the flock. But the eagles were quietly perched in spruce trees on shore. The perpetrator of the panic was a male harrier that coursed low over the flock, briefly followed the birds around the point, and then turned to follow the beach, perhaps looking for something of a more convenient size. Could a harrier actually take a scoter that weighs twice as much as itself?

On the way back up to the parking lot we noticed quite a few flowering fern-leafed goldthread; close inspection showed that all of these were male. Maybe those that also have female parts (that is, they are hermaphrodites) flower a little later?

 

Finally, as we left the parking lot, we spotted a snowshoe hare scampering up the bank. Not white, not brown, but in between, and not well camouflaged in any habitat. Although I’ve seen thousands of hare tracks, one dead leveret (baby hare) in the jaws of a cat, and one dead adult hare in the clutches of a goshawk, I can’t remember seeing a living adult hare around here. So this was a minor coup.

During our short perambulations on the beach, we also filled a yellow litter bag to the very brim, with cast-off food and drink containers, oil rags, broken plastic parts of unknown objects, and a thick, sodden seat cushion. The bag containing all that mess we deposited near the trash container at the trailhead. However, on the shore of Shaman Island there was a wheel, with tire, that was too much for us to carry out; we hope some kind soul with a boat might go and remove it to a more suitable location.

PSP and wildlife

how animals deal with one of nature’s potent poisons

Not long ago, I sat on a rock near Auke Rec, watching a squadron of scoters busily diving for mussels. They weren’t doing their coordinated, follow-the-leader diving; each bird was on its own, going down to pull up a mussel.

White-winged-Scoter-male-with-mussel-by-bob-armstrong
Photo by Bob Armstrong

That made me recall that spring and summer are usually the times when there are plankton blooms. Along with those events, we usually get reminders about the risks of paralytic shellfish poisoning (PSP). In fact, there was a piece in the Empire some days ago and several warnings on the radio about the unpleasant, sometimes lethal symptoms and noting that cooking does not disable the toxins. Historically, PSP has caused several episodes of multiple human deaths in Alaska.

The tiny organisms in the plankton blooms produce several kinds of toxins. Those that cause PSP are neurotoxic, affecting the nervous system (in multicellular animals that have nervous systems). Nerve impulses require the movement of sodium (and, in some cases, calcium) ions in and out of cells, and the neurotoxins impede that process. So afflicted animals can suffer numbness, paralysis, respiratory failure, and eventually death.

Plankton blooms occur when the water temperature and light are suitable and when nutrient levels are high (which commonly occurs when there is spring runoff from glaciers and freshwater streams). Among the many single-celled organisms that respond in ‘blooms’ are some that are known as dinoflagellates (referring to the whiplike ‘tail’ or flagellum that whirls to propel the cell along). There are hundreds of kinds of dinoflagellates; some are photosynthetic, some are predatory, and some are both.

Many species of dinoflagellates produce toxins of various sorts (in addition to those that induce PSP). Why do they do this? Perhaps as a means of defense against other small organisms that would eat them. Another possibility is that exposure to such toxins in the water might help a predatory dinoflagellate to capture its prey—slowing the prey’s swimming speed, perhaps immobilizing it. So the toxins are always present, but usually at low concentrations—until there is a bloom, and the toxin-producers become very abundant. A recent study showed that a particular dinoflagellate (belonging to the genus Alexandrium, which is said to be the genus most involved in toxic blooms in Alaska) increased its toxin production in response to acidified waters and low phosphorus levels, so that opens the door to potential increases in toxic blooms in the future, as ocean acidification increases (this finding should be verified by additional studies).

After watching those scoters gobbling up mussels, and thinking about the well-advertised effects of PSP on humans, I wondered about the effects of PSP on other, non-human organisms.

When there is a plankton bloom, and toxin-producing organisms are very abundant, all the numerous marine creatures that eat plankton consume vast quantities of the toxins. Many bivalve shellfish (clams, mussels, scallops, etc.) are filter-feeders, sifting plankton from the water, and they can accumulate high concentrations of the toxins. Sometimes the toxins are sequestered in certain parts of the shellfish body, such as the siphon. In some cases, the toxins may be stored for as long as two years (e.g., in butter clams), prolonging the possible effects well beyond the time of the bloom itself.

Do the dinoflagellate toxins poison the invertebrates that eat the dinoflagellates? Potentially, yes. But at least some plankton-eating invertebrates have ways of avoiding serious harm. The softshell clam, for example, develops resistance to the toxin produced by a particular dinoflagellate when it is exposed repeatedly to that toxin. This implies that the biological reason for resistance is that the toxin is damaging; otherwise, why resist? Some plankton-eaters can avoid the toxins by feeding selectively, rejecting potentially toxic dinoflagellates. For example, the Pacific oyster and the northern quahog can simply shut down feeding activity when presented with Alexandrium prey. However, this is not a direct response to the toxins themselves, but rather to the toxin-producer: even non-toxic Alexandrium strains produce the shut-down. In other cases, dinoflagellate toxins can be very damaging to larval invertebrates of several kinds. I find myself wanting to know a lot more about the physiological effects of dinoflagellate toxins on invertebrate consumers and the responses of the consumers to the presence of toxic prey.

Many marine creatures consume the plankton-eaters. Predatory snails that drill into clams or mussels can ingest toxins from the flesh of the prey. Crabs that prey on small molluscs can ingest the toxins too. Zooplankton and small crustaceans, such as krill, consume other plankton and thus become vectors for the toxins. Lots of species of small fishes consume plankton: e.g., sardines, anchovies, sand lance, herring, mackerel, young salmon. Sometimes the level of toxicity is sufficient to kill these fish, and die-offs have been recorded.

Of course, the toxins can move on up the food-chain, when the fish-eaters consume fish that have eaten toxic organisms. When the fish-eaters swallow the whole body of the prey, they obviously get the toxins even if the toxins happen to be only in the digestive tracts of the prey and not throughout the body. The concentrations of toxins tend to increase, as they move up the food-chain. There are numerous records of massive die-offs in North American waters of fish-eating marine birds (terns, gulls, pelicans, scoters, cormorants, murres, loons, etc.), and no doubt many unrecorded incidents of nonlethal illness. Marine mammals can be seriously affected too, including sea lions and humpback whales. Interestingly, sea otters are reported to able to detect the presence of PSP toxins and discard to most toxic parts, or at least just not eat so much. Butter clams are a favorite food of sea otters in some areas, and there the otters can just reject the siphon and other parts where the toxins are concentrated.

Gambling on Berners Bay

playing the annual wildlife lottery

Going to Berners Bay in spring is always a bit of a lottery—you never know what you might see there. Maybe nothing much, except some scenery. But if you hit it just right, things can get pretty interesting.

When the eulachon (a.k.a. hooligan) are in the bay, staging for their spawning migration up the rivers, there might be dozens upon dozens of sea lions, foraging cooperatively and rafting up to rest from their exertions. Harbor seals would be there too, in quantity, and humpback whales would be likely to cruise through. Orcas may arrive, in search of unwary sea lions or seals.

Once the hooligan are in the rivers, the action in the bay dies down. Tens of thousands of gulls and ten hundred eagles gather to gorge on these oil-rich, slow-swimming fish, which run a fearsome gauntlet of predators in the lower reaches of the rivers.

Springtime also brings shoals of herring, which often spawn in the bay. That draws lots of eagles, which line the shore and swoop down to snag a distracted spawner. Gulls feast on the eggs that coat the rockweed in the intertidal zone, and humpback whales come to fill their maws with fish.

One year, our annual kayak junket to Berners Bay happened when both hooligan and herring were bringing in hordes of predators, and the bay was a crazy place. We hardly knew where to cast our watchful gaze!

This year, 2011, was different again. The eulachon were up the rivers, attracting clouds of gulls, and only a few sea lions and seals remained in the bay. The herring had spawned recently, and their eggs glistened on the rockweed when the tide went out. The gulls were all busy with the hooligan in the rivers and ignored the herring eggs, and the mobs of eagles were notably absent.

Instead, we saw acres and acres of surf scoters—there must have been ten or twenty thousand of them. What a racket! They spent a lot of time apparently loafing and talking. Every so often, a group of them would head to the shore and nibble on herring eggs, sometimes pulling off chunks of seaweed too. I suspect they were also diving for mussels. Or they would suddenly all dash across the water with great splashing, for no apparent reason. When thousands of ducks do this all at once, it creates quite a ruckus.

Bonaparte’s gulls were diving after pink salmon fry that thronged the shallows and maybe also juvenile herring in the deeper water. Barrow’s goldeneyes in small squadrons swam along the rocky shore, gobbling up herring eggs. A kingfisher dove repeatedly and seemed to catch a salmon fry on almost every try. Three solitary black bears foraged on separate beaches.

A little walk in the woods produced three very dead and dried herring, perhaps dropped by some inept or unlucky eagle or gull. Another possibility, however, is that ravens had grabbed a fish as it tried to spawn in shallow water, or had stolen it from another bird, and stashed it in the trees. Years ago, when I was studying predators at the eulachon run, we noticed ‘rains’ of dead eulachon falling from the trees when the wind blew; they’d been stored up there by a gang of scavenging ravens.

Another stroll in the woods found us in a soggy little opening where lots of skunk cabbage grew. But instead of a cheery array of bright yellow, there were only stubs barely showing above the muck. Something had messily chawed them all off, right down to the mud line. The culprit left evidence of its passing: huge cloven hoof prints and occasional clusters of digested pellets about the size of the end of my thumb. Moose were introduced to the Berners Bay area some decades ago and they have found a nice smorgasbord there—we also noted well-browsed alder shrubs along the upper beach.

So, although we missed the show at the hooligan staging in the bay and the show at the spawning herring, we found plenty to see!

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!

Autumn is here in earnest

the subtle fruits of a somber season

We pass the autumn equinox, and the days get ever shorter. They’ve been getting shorter ever since late June, but now we really begin to feel it. The fall rains are here, and when we look out our windows, we see gray gray gray. It’s seldom as bad as it might look, however, so it pays to get out and about.

In fact, I think that getting outdoors is an important part of living with short days and gray skies. Some folks flee the fall and winter by going south, but I have found several ways to enjoy staying here during those seasons. I try to get outdoors every day, talking a walk on one of our trails; maybe not a long walk, but I’m out in the fresh air, seeing something besides four walls. I sometimes play a game with myself: the challenge is to find at least one thing (preferably three things!) of esthetic or natural-history interest. Sometimes these things are connected: I like to recall the visiting musician who took a walk in the forest and found that the rich variety of green tones in the mosses and ferns reminded him of a piece he had just played; now every time he plays that piece, he’ll see the rainforest. I greatly enjoy the rich cultural life in town, especially the music; the visual and thespian arts are also alive and well, and various lecture series can be both instructive and entertaining. Also, I do best when I have a project or two to work on; it doesn’t much matter if it is writing or building bird houses—a project that engages what’s left of my aging mind.

When I’m out, there are actually several autumn things to look forward to. Great rafts of scoters gather in the coves and channels. It is fun to watch them do what I call ‘chain diving’—a whole line of scoters dives, one after the other, in the same spot; then they all come up, one at a time, a little farther away. I have not yet found anyone who can tell me exactly what they are doing or what food they might be finding or why they do it in that way.

Out on sandy, gravelly bars, there might be small flocks of shorebirds that spend the winter with us. Rock sandpipers and dunlins often hang out together. Adults in breeding plumage of both species have black belly patches, and some show the black blotches as winter goes on, so look closely to distinguish them. These shorebirds breed on the Arctic tundra of western and northern Alaska. Sometimes there are surfbirds on rocky reefs and points; they nest in alpine tundra of Alaska and the Yukon. I occasionally flush a solitary snipe, not only in the marshes and swamps where they might have nested but even along streams in the forest.

I look forward to spotting the first slate-colored juncos that arrive at the bird feeders; they come from the Interior to spend the winter with us. Oregon juncos live here all year but mix with the slatey ones in winter. At present, both kinds of juncos are classified as the same species but different subspecies or races.

Thinking about Oregon juncos reminds me to ask a question: these birds are distinguished from slate-colored juncos in part by a chestnut-brown back. Likewise, our chickadees have chestnut-backs that are lacking in the other North American chickadees. Is there a particular reason why chestnut backs are popular here? Is there something about rain forests that favors that plumage pigmentation?

Of course, the black-billed magpies come to us in the fall too. They temporarily monopolize bird feeders, tease the eagles, and sample leftover salmon carcasses. On a rare sunny day, the iridescence of their black feathers makes them quite spectacular.

Flowering season is over in fall, but you might spot a few late purple asters alongside the trail. Behind the Visitor Center at the glacier, there has been a very late blooming Romanzoffia sitchensis (the common name is Sitka mist-maiden). In the muskegs, look for tiny yellowish cups that might be mistaken for flowers. These are the seed heads of the swamp gentian. Each two-parted cup holds a little cluster of seeds; when a rain drop hits the cup, the seeds get splashed out and so dispersed. This ‘splash-cup’ dispersal is not common, but it is shared by the bird’s nest fungus.

Sept-11-Dan-Moller-11-Gentian-seed-pods-resize
Gentian seed pods

One of my favorite things to do is watch the coho arrive in local creeks. When they do, the bears—which have been waiting for them, ever since the sockeye run ended—get busy again in the streams, and that makes for great bear-watching. I think that many of our local bears really depend on coho to ‘top-up’ their fat deposits in preparation for hibernation. The amount of fat laid down in fall is important in determining how many cubs a female bear can feed while they are in the winter den and it is probably important for winter survival of juvenile, subordinate bears that are not yet expert foragers.

I don’t know all the factors that regulate the size of coho runs, but there is evidence that juvenile rearing habitat is one important factor that helps determine the size of a local coho population. Incoming adult salmon are commonly able to slither over or jump over most beaver dams, so dams seldom limit the spawners. However, juvenile coho rear in pools in streams and in beaver ponds, and research has shown that they grow really well in beaver ponds. Down in the Pacific Northwest, biologists have even re-introduced beavers to certain stream systems, so that their ponds will increase the available rearing habitat for salmon and help restore the diminished populations. Because salmon typically return to their natal stream when it is time to spawn, juvenile rearing success helps determine the size of the spawning run. Thus, when beaver dams are removed from streams where coho spawn (so that their ponds are drained), or when beavers are trapped out of a system and their dams (and ponds) are no longer maintained, and rearing habitat is thus reduced, there is reason to expect that the coho population of that stream will decrease. And that leads to the expectation that the bears living in the area would lay down less fat, possibly survive less well, and produce smaller litters of cubs.

Fritz Cove

wildlife spotting and speculation along a quiet stretch of highway

It was murky sort of day, low overcast, occasional rain squalls, and sloppy snow underfoot. Our schedules didn’t offer many breaks either, so we opted for an easy walk along the North Douglas Highway.

The beach by the North Douglas boat ramp could well be called our very own ‘Skeleton Coast’ (with apologies to southwestern Africa), for the number of picked-over, disassembled deer carcasses reposing on the cobbles. Two eagles each claimed a deer head, while ravens, crows, and gulls squabbled over the few remaining scraps.

A couple of humpbacks cruised and dove, attended by a small gang of sea lions. Either the whales weren’t stirring up much tasty fare for the sea lions, or they had already provided very well for the ‘lions, which spent a good deal of time lolling about, floating belly-up or side-up, poking out a fin or two occasionally.

We counted nineteen kinds of birds (and there may have been more). All the usual suspects were there. We watched a red-throated loon with a long, wriggly fish, which was finally subdued and swallowed. There were a few Pacific loons and what we thought was an immature yellow-billed loon. A duo of common murres was a nice surprise. The only songbird was a song sparrow, which—around here—could well be called a beach sparrow.

A mixed flock of numerous scoters included mostly surf scoters, some white-winged scoters, and a probable black scoter. The scoters were diving, apparently for mussels. Most of the birds were diving independently of each other, with only a few of their famous chain-dives (in which a whole line of birds all comes up a spot where, one by one, they go down; a little later they all come up, one by one, at another spot a short distance away. I’ve never been able to find out why they do that.)

Several glaucous-winged gulls were hanging out with the scoters, mostly behaving very casually and innocently, floating around together. But every so often, a gull pounced on a scoter that was just coming up with food in its bill. At least some of those pounces made the scoter release its catch, to the benefit of the piratic gull. But many attempts at piracy seemed to fail. More puzzling was the observation that a gull would jump on the back of a floating scoter, forcing the scoter under the surface. Are the gulls trying to make the scoters dive for food or are they just having fun?

A few days later, it was still raining, and blowing, and I stopped at the North Douglas boat ramp. I was attracted by dozens of crows in the parking lot and on the cobbly beach. I pulled up near the far end of the lot, away from the crows, and just sat there to watch what was happening. It soon became clear: the crows were collecting small mussels from the beach, flying up and dropping them on the hard blacktop surface (and on the beach cobbles). By careful watching, I determined that sometimes a mussel shell cracked after one drop, but sometimes it took four drops of the same mussel before the crow could gain access to the soft interior.

crow-with-mussel-by-bob-armstrong
Photo by Bob Armstrong

The height of the drops varied greatly, from about five feet to maybe twenty feet or so, and longer drops seemed to be more effective. But a high-flying crow took longer to descend to its prey, which gave other crows time to sneak in and appropriate it. There were many attempts at stealing food from each other, so theft was a real risk. There was a trade-off between effective cracking and protecting the prey from competing crows.

I would love to know more about the energetics of this behavior. Flying up and then zooming down to protect the food takes energy. If a crow has to fly up three or four times, does the energy in one mussel fully repay that effort? Once a mussel shell cracked, the crows would poke and pry to extract the insides, often holding down the shell with a foot. Can crows wrench out the strong muscle that bivalves use to shut the shell—that muscle is very tightly attached to the shell, or can they only feed on the other organs?

This was also a bathing place for the crows. A pothole in the blacktop had collected rainwater. It was big enough for two crows to fit in at the same time, with much exuberant flapping and splashing. Occasionally several crows would line up politely to have a turn at their public bath. Bathing was not as competitive as feeding!