a heron in the forest, a frozen feast, and raven excavations

The first halfway decent snowfall in mid November drew me out to look for animal tracks and anything else of interest. I went with a friend to the forested banks of the lower reaches of Eagle and Herbert rivers. Deer, both big and small, had wandered extensively throughout the area. Mink had a regular route along the top of one river bank. Porcupines had been out before the snow stopped falling, but squirrels left very fresh prints. Just as we were commenting on the lack of bird tracks, we happened upon some clear prints left by a heron strolling through the forest.

Then we heard a ruckus made by some squabbling ravens, over on a sandbar across the river. We approached quietly, with several trees (and the river) between us and the gang of ravens, but they spotted us immediately and took off. A number of magpies then moved in. The big attraction was the bony torso (spine and rib cage) of a deer, already well picked-over but still clearly worth serious attention. We settled down among the trees to watch.

We counted at least nine magpies; the precise number was not readily determined, because they were constantly flying to and fro: pecking and tugging briefly, then departing for a few minutes, and returning to grab another morsel. Were they caching these little bits of meat or just going off to eat each bit in peace? All those magpies seemed to be able to forage together without altercations (unlike the ravens); there apparently was room around and even inside the rib cage for them all.

A juvenile eagle arrived, briefly scattering the magpies, but they soon moved in again—on the side of the carcass away from the eagle. This was not very profitable feeding for the big bird, however, and it soon departed. Meanwhile, one or two ravens cruised by, or perched up in the spruces, occasionally hopping over the sand toward the bones but nervously taking off without feeding there again. Maybe nine magpies were too much for them, but I think they knew we were still there and did not like being watched.

A few days later, we had wonderful snow and lots of it. Spruces bore thick white blankets on drooping branches and alders bent almost to the ground under the heavy load. Rather than do the various tasks I was ‘supposed’ to do, I took off out the road to do a little exploring on snowshoes. ‘Twas the first time on ‘shoes this season, and it showed (sadly). Tracking was good, however: fresh deer trails, old otter slides leading from one patch of open water to another, not-so-old porcupine trails, deeper than the otters’ marks, a few squirrels, and a mink.

Two ravens were assiduously digging in the snow, in selected spots, tossing snow aside with their bills. Sometimes they dug down several inches, apparently getting very small, unidentifiable items. What could they be finding, and how did they know where to dig? I shared a few crumbs with them.

That lovely snow didn’t last, here near sea level. But I sure liked how it brightened up our short days!

Sunflower sea stars

big, fast, and flexible

One day in March, I walked a local ‘pocket’ beach. Among the accumulated crab claws, fish bones, rockweed bits, and mussel shells at the high tide line were two disarticulated arms of the sunflower star. (Sea stars are not fish, so the old name of starfish is obsolete.) I don’t know much about this (or any other) sea star, so I set out to learn a little.

Sunflower stars range from the Aleutians to Baja, usually in the subtidal or lower intertidal zones, but sometimes much deeper—down to several hundred feet. Unlike other sea stars, they are quite soft-bodied and flabby. All the tiny bones that link together to make other sea stars firm and nearly rigid are only loosely connected in sunflower stars. Instead, the sunflower stars depend on internal fluid pressure to maintain their body form and probably also get some support from the water they inhabit. This arrangement may prevent them from using upper intertidal zones that are frequently de-watered and may get them into trouble if they accidentally find themselves in the upper zones without access to water; among other dangers, they would be exposed to freezing temperatures that could be harmful.

Photo by Kerry Howard

These are arguably the largest sea stars in the world, sometimes well over three feet in diameter. Adults can have up to twenty-four arms, although the juveniles start with just five and add arms as they grow. All those arms bear thousands of tube feet that are used to cling to rocks or clam shells or even to dig pits in the sediments to nab a buried mollusk. These sea stars can move rapidly (for a sea star)–over three feet a minute, and they sometimes travel several kilometers.

Sunflower stars are voracious predators (and scavengers) that eat almost anything that moves, including sometimes each other, and even some prey that doesn’t move. They can evert their stomach and wrap it around a prey, digesting it externally. Or they can engulf a prey with their mouth and digest it internally. We once found a big sunflower star that was stranded in the upper intertidal zone with a sizable cockle still held in its mouth.

These sea stars could be called the Terror of the Subtidal Zone. They are capable of stripping a wide area of all the resident sea urchins, a popular prey. Many of their prey animals can detect the approach or the touch of this predator and take evasive action: moving higher in the intertidal or burying themselves deeper in the sediment. Sea cucumbers twist and squirm and try to swim away. Some snails clamp down on a rock or retract entirely into their shells; some exude a noxious slime that has a deterrent effect. Cockles turn somersaults and try to roll away. Despite numerous observations of the escape behavior of the prey, I have not found much information on the relative success of different tactics. One study compared the defenses of two species of sea urchin: One species tries to ward off a sunflower star with long spines, and that is more effective than the tiny pincers employed by another kind of urchin.

Sunflower stars typically spawn in spring and summer, occasionally in winter. They are broadcast spawners, shedding their eggs and sperm into the water. To do this, they are reported to stand up on the tips of their arms, raising the body above the substrate, so the gametes flow down into the water or onto the substrate. Stars can not only regenerate a lost arm or two, but if they are more seriously fragmented, the fragments reportedly can regenerate the missing parts and reconstitute whole stars.

Sunflower stars are aggressive beasts, seldom tolerating closeness of other sunflower stars or stars of other species, but they are occasionally found piled up together, for reasons that don’t seem to be clear. They appear to be susceptible to certain diseases or other afflictions: a major die-off was reported off the coast of Vancouver Island last year. Their predators are few but include large gulls, big crabs, and the morning sun star. These may harvest just an arm or two, leaving the sunflower star to regenerate new arms.

Frosty paradise

so many varieties of ice crystals

The trail through Cowee Meadows to the cabin and the beach has seen significant improvement (thank you, State Parks!), with more to come. In midNovemeber, red squirrels were belatedly and busily carrying nest material for a winter snuggery. There were a few gulls and harlequin ducks in the bay, and an intriguing pile of feathers on the trail, where a predator had plucked its prey.

For me, however, the frost patterns stole the show. The wide meadows were a truly spectacular sight, with hoar frost on every available surface. Cow parsnip was ‘flowering’, far more beautifully than in summer—every tiny sprig on the dried inflorescence wore a tuft or ruff of crystals, and every old flower head in the meadow was frost-flowering. Out near the beach, sweetgale twigs bore large frost tufts at the tip and every wee bud along the stem had its own crown of frost. Yellow-rattle stems held puffs of frost on every empty seed pod, and the arching valves of split-open fireweed seed pods made lovely patterns.

In the woods along the trail were odd, linear, fluffy-looking patches of white, some of them several inches thick. Not snow, of course, because that hadn’t yet arrived at low elevations. Most of these fluffy patches were on the ground, but a few had developed on thin, small snags. A close look revealed that all of these patches had a piece of wood underneath. Some had long, thin, frosty curls emerging in dense clusters from the sticks, while a few held crowds of shorter, thicker crystals. I think that our freezing temperatures in the middle of November caused water in the soggy sticks to freeze and expand, extruding these crystalline forms. We often see thick columns of ice being pushed up out of freezing mud in the same way, but these fuzzy, frosty sticks are much rarer.

On a previous day out on the wetlands, I noted the numerous seed heads of some fine grasses, arching over so that their frosty seed heads made a crystalline canopy. And along some mudflats next to the Mendenhall River there was a fascinating layer of very thin ice on which were traced very unusual patterns of paisley and celtic knots.

Crystals on a bud. Photo by Bob Armstrong

Looking closely at the hoar frost on bridge railings near the glacier revealed an astonishing array of forms. Even without a microscope, I could see intricate variations within the superficially uniform spikes of frost that coated the wooden rails. Some were columnar, often with candelabra-like branches. Others were composed of small, flat plates neatly stacked on their edges, or somehow held in a ladder-like arrangement. Some plates had extremely fine filaments around the edges. Still others spikes were made of angular, linear crystals lined up at right angles to each other. And so on! Next time we get a good crop of hoar frost, go and see for yourself! It’s a real visual treat.

Lazy day at Crow Point

porcupine shelter, bear sign, and winter berries

The tide was just starting to go out, leaving elegant wave marks in the sand. Otter and mink tracks were barely discernible amid the evidence of the passage of booted humans and their happy dogs. At the mouth of the river, a little cluster of gulls flitted up and own over the heads of two seals; there was obviously something edible there. A few buffleheads and a solitary Barrow’s goldeneye cruised the lower reaches of the river. Canada geese honked their way up the river, two by two; could they already be thinking about nest sites?

We found an old stump under which a porcupine had sheltered. A sizable pile of scat pellets filled a depression under the arching roots, and back in a corner, a cubbyhole offered protection from wind and rain. These pellets were more rounded, less oval, than usual for wintertime scat of porcupines, but we couldn’t think of any other creatures that would leave a latrine like this.

Possibly the most interesting observation was evidence of bear activity. In late February, this is a bit unexpected. But in this goofy pseudo-winter we are having, some bears in town have continued to be active and apparently never denned up to hibernate. So maybe all the signs of digging and eating out here fit right in with our mild weather.

In some places, the vegetation had been roto-tilled with shallow scoops that overturned mosses and roots. It wasn’t always clear what the foraging bear was seeking, but in several spots we found the exposed roots of chocolate lily (a.k.a. rice root). However, in each case, only some of the root material had been removed, leaving much seemingly edible stuff behind. That’s a little mystery that we’ve seen on several occasions—why dig it up if you’re not going to eat it?

A couple of bear scats contained only vegetation fibers. One also held partly digested highbush cranberry fruits. Because bears have short digestive tracts, food often passes through fairly quickly, and whole berries commonly come through. Another scat contained plump, juicy, bright red (undigested) berries of the plant called false lily of the valley (a terrible name! this plant does not resemble the real thing at all.)

The grassy berms behind the beach at Crow Point provide excellent habitat for false lily of the valley, and there was an abundant berry crop on view. Last year’s dead, heart-shaped leaves were gray, with black veins, and they set off the glowing red berries. These berries don’t get their fully ripe, bright red color until they’ve been well chilled. So berries produced last summer are conspicuous after a cold season and are then available for spring-arriving birds. It is interesting that this bear had not focused on the many berries that bejeweled the ground, but instead had spent its time digging.

Over a hundred Canada geese grazed in the broad tidal meadow. By walking close to the trees, we managed not to disturb their foraging. A few alert heads popped up to check us out but soon went back down to the business of eating. Earlier, an eagle had caused much consternation in this flock, but our passage left them calm.

While we were ambling down the beach, a stormlet blew in from the south, the sharp wind stirring up growing whitecaps. We were glad to put the wind at our backs when we left the beach to circle the grazing geese. Parka hoods up, shoulders hunched, we put on our ice cleats to trudge the icy trail back to the car.

Barn swallows and thixotropy

dabbing and daubing for stable nests

One day in early September, I was fascinated by a pair of barn swallows still feeding big chicks in the pavilion by the visitor center. All the other pairs there had long since fledged their chicks, and those chicks would be experienced foragers by the time of migrations to southern climes. The September chicks would leave the nest soon, but they would have a lot to learn about catching insects on the wing, and it seemed unlikely that they’d be proficient foragers by migration time. An uncertain fate!

As I looked at that nest, I began to wonder about how barn swallows manage to build such a nest. Their nests are shallow cups made of little mud balls stuck together, and lined with feathers. Their relatives, the cliff swallows, build a more elaborate, gourd-shaped nest with a narrow entrance, but they use the same basic technique—mud pellets stuck together and the whole edifice stuck to the side of a building or cliff.

But what makes the pellets stick to each other? In a nest under construction, the first pellets to be placed have had a chance to dry a little, and when they dry, they shrink a bit. If a swallow just plopped new, wet pellets into place, the shrinkage rates of the new and old pellets would differ, and this creates weakness and cracks in the structure (a result well known to human potters). Not a good result.

That’s where thixotropy comes in. It’s a fancy but concise way of describing what happens to some seemingly stable materials when they are mechanically agitated. They become fluid, temporarily, and a little later become stable again, often in a new configuration. It turns out that thixotropy (from the Greek words for ‘touch’ and ‘change’) is characteristic of many materials and situations. It’s involved with some metal casting, certain printing processes, and some foods, for example. Perhaps most famously, it can happen during earthquakes, which shake and liquefy wet soils, causing buildings and trees and everything else to sink or tip or slide, sometimes catastrophically.

Animals use this curious phenomenon too. When bald eagles dance up and down on wet sand in order to capture buried sand lance, one effect of their prancing is liquefying the sand, making the fish more accessible. Gulls can use the same trick.

Mud dauber wasps build little cells of mud, stuck to walls. When they add new pellets to the cells, they add a bit of water from their crop, and they buzz. The vibrations liquefy the mud, letting it spread into the earlier, drier pellets. Then old and new pellets vibrate together, achieve the same consistency, and are stable when vibration stops.

Gathering mud. Photo by Bob Armstrong

That brings us back to barn swallows. They collect mud pellets from puddles and gradually add several rows of pellets to form the nest cup. But they apparently don’t just whack each new pellet into place. Instead, when they add pellets to the growing base, they use a dabbing or dabbling motion. This jiggles the old (drier) and new (wetter) pellets until the water content is similar and their consistency is equalized. As soon as the dabbling stops, the junction of new and old pellets becomes stable. Wouldn’t it be fun to find out if young adult barn swallows know to do this automatically or if they have to learn the hard way (if their first nest-building attempts collapse)!

Barn swallows

a complicated society

I like to go up around the Mendenhall Glacier Visitor Center for lots of natural history reasons, and one of them is to watch the barn swallows that nest in the pavilion, the bus shelter, on the sides of the center itself, and sometimes on the kiosk. The insect-catching adults swoop high and low, sometimes playing ‘chicken’ with the numerous cars and buses, which typically exceed the posted speed limits. Most of the thousands of tourists are oblivious to these birds, but a few do pay attention.

In mid July, some of the nests had big chicks, either just leaving the nest or just about to do so. Other pairs still had eggs, in some cases because vandals had destroyed their first nests and these pairs had to begin anew.

Photo by Bob Armstrong

Originally, barn swallows nested in caves, cliff crevices, and hollow trees, but now they have converted to using human structures almost entirely. They build inside culverts, under bridges, and on buildings; use of natural sites has become unusual and noteworthy. Historically, as North American became more populated by humans, barn swallows also spread into new areas.

Barn swallows occur all over the northern hemisphere in the nesting season (but migrate to South America or Africa in winter), and they are among the most intensively studied songbirds. European birds have white breast and belly feathers, but in North America these feathers are rusty orange. It turns out that in North America, a dark rusty breast on a male is attractive to females, and females mated to dark rusty males produce more chicks than those mated to paler males.

In this species, the elegant tail is long and forked, and males have longer tails than females. A deeply forked tail is said to increase lift and allow tighter turns, and if the fork is symmetrical, maneuverability is enhanced. Long, symmetrical tails develop on males that have few external parasites. Females really go for males with long, symmetrical tails—the best fliers with the fewest parasites. So males with such tails have a high probability of getting a mate, they get better mates, and they indulge in more extracurricular copulations as well. Females that are socially bonded to short-tailed males actively seek extra-pair copulations with better-endowed males.

However, those studly males with big tails don’t invest much time and energy in the chicks of their ‘official’ mate: they’re too busy running around. The short-tailed males are more attentive fathers; they also reportedly build better nests, and females are also more attentive moms when they have better nests. So there is some compensation to females for not being mated to the studliest guy. But the nests of short-tailed males often contain some other male’s chicks, so the short-tailed males end up investing effort in chicks that are not their own.

If all that were not enough complexity, barn swallow nests are sometimes subject to hostile takeovers by intruding males. The marauding male may belong to another species, such as a wren, or house sparrow, or cliff swallow. And sometimes the intruder is another barn swallow. If the intruder pushes out the original male, he generally destroys any eggs or small chicks, and then mates with the widowed female.

Nests are built of pellets of mud, cemented to the wall or beam, and lined with grass and especially feathers. Both parents incubate the eggs, although only the female has a featherless, highly vascularized brood patch on her belly. Incubation takes about two weeks and chicks are in the nest roughly three weeks. After leaving the nest, the juveniles are tended by their putative parents for about two more weeks. Chicks in a second brood are sometimes also tended by older siblings from the first brood. Parents (and older sibs) can recognize their fledglings, not by voice, but by variation in plumage color patterns on the chest—no two chicks are exactly alike.

Barn swallows nest in several locations in Juneau and are easily seen. Next time you see one, just think a moment about how complex their lives are.

Canada geese

migrants and residents among us

Most folks love to hear flocks of Canada geese flying overhead, especially in spring when the northward migrations pass over Juneau. Sometimes the flocks land in local wetlands to feed, fueling the next leg of the journey.

Photo by Bob Armstrong

On a mid-February hike near the scout camp, a small group of geese foraged in the meadow, and we managed to circle around them without sending them into an alarmed flight. Another small group flew in to join them, talking constantly with each other.

Several of the hikers remarked that it seemed rather early for the migrating flocks of geese to be here. Indeed it was! The geese we saw belong to a distinct sub-species, known as Vancouver Canada geese, that occupies Southeast Alaska and British Columbia year-round (although a few may migrate). In winter, we often see these residents on wetlands and in estuaries along Juneau shores. For instance, Echo Cove, the Cowee Creek estuary, Eagle Beach, the Mendenhall wetlands, and the Lemon Creek wetlands are often good places to see them.

Vancouver Canada geese are unusual in several ways (in addition to being here all year). They are larger than other subspecies of Canada geese; adults weigh an average of six to ten pounds in fall but even more in spring. And they nest in wooded areas, not in open areas such as marshes and tundra—habitats that are more typical of other subspecies; in short, Vancouvers have adapted to the commonly available habitats here in Southeast.

Nests are usually placed at the base of a pine or a group of pines in muskegs or at the base of a spruce or hemlock in denser forest. But sometimes, the nest is on a snag or even in a live tree. Nest sites can be far from tidal waters and are not usually adjacent to freshwater ponds; the nearest open water is likely to be a small, shallow forest pool. Whereas other Canadas escape to open water when disturbed, Vancouvers flee to cover in the forest. During the incubation period, the male may stand guard while perched high in a nearby tree; those great webbed feet somehow manage to let a big goose perch on a branch!

Other than residency, habitat, and body size, Vancouvers are much like the rest of the species. Males and females have similar plumage, but males are slightly larger. They reach breeding age in two or three years after hatching. They form long-lasting pair bonds; but if one member of a pair dies, the widow(er) may find a new mate. Each pair sets up a nesting territory, excluding other pairs.

Females do the job of incubating the eggs, for about four weeks, while the male keeps watch. There are usually four to six eggs in each clutch, but the average clutch size is smaller in nests that are started later in the season. Not much is known about nesting success, in part because the birds are so secretive and nests are hard to find. Even with radio-tracking, finding nests takes considerable effort. So it seems that only two studies of nesting success have been done, both on Admiralty Island, and the sample sizes are small (fewer than twenty-five nests in each study). A study in the 1970s found that eggs successfully hatched in fifty-six percent of monitored nests, and a later study found that about eighty percent of nests survived to hatching time. These estimates lie within the range reported for other populations. Canada geese whose nest is destroyed can sometimes renest in the same season, but the clutch size is smaller and obviously hatching time would be delayed. So juveniles would not be as well-developed when fall comes, but the consequences of such a delay have apparently not been studied.

After the eggs hatch, the goslings are able to walk, swim, and forage within a day’s time. They are guarded by their parents, which call out alarms if disturbed and shoo the young ones into cover. Sometimes, several broods of goslings are gathered together in what is called a crèche, and all the parents attend them. Goslings are able to fly after about eight or ten weeks, but they stay with their parents for a year.

After the nesting season, the geese molt and become flightless for several weeks while new flight feathers grow in. At least in some cases, birds seem to have favorite molting sites, probably not terribly far from where they nested, where they gather in flocks. I’ve paddled into Wachusett Inlet in Glacier Bay, for instance, and found the water surface littered with goose feathers (I soon retreated, so as not to disturb any still-flightless birds).

Canada geese are herbivores, eating a great variety of vegetation. Grasses and sedges are a mainstay in summer. In Southeast, a favored summer food is skunk cabbage leaves, but they also eat blueberry leaves and fruits and other things. On local wetlands, we have found evidence that they dig up the underground parts of silverweed, and in winter, we see them grubbing up the underground parts of sedges. We have sometimes found scats filled with poorly digested moss, which seemed unusual. The digestive system of these geese is not highly efficient, despite a good gizzard and a substantial microbial flora in the caecum and intestines, so they have to eat a lot.

Based on aerial surveys, the population of Vancouvers in Southeast is estimated to be about twenty thousand or a little more. It appears to be fairly stable, perhaps partly because it is not subject to excessive hunting pressure; historically, other populations in Alaska have crashed because they have been overharvested (in the Yukon-Kuskokwim area) or devastated by introduced foxes (on the Aleutians).

Thanks to Debbie Groves, US Fish and Wildlife Service, who provided several useful references.

Eating lichens

it helps to have four stomach compartments

Photo by Bob Armstrong

Mountain goats appeared on the cliffs near Nugget Falls in February, as they often do. My occasional visits to the area have revealed two females and one juvenile, sometimes feeding on alder twigs and once I saw an adult engulf a whole conifer branch. They also nibbled on mosses and lichens close to the ground; we could see that one of their choices was the white foam (or snow) lichen (Stereocaulon).

Here in Southeast, deer, moose, and goats commonly eat lichens, especially in winter when there is no greenery. I’ve seen browse lines in the forest, where deer have munched all the hanging lichens (such as witch’s hair, Alectoria) up to a certain height. Up north, and across the Arctic, caribou and reindeer depend on lichens; in winter they dig away the snow to reach lichens on the ground.

These observations begged the question: What nutrition do lichens provide? Most lichens are low in protein (around two percent) but offer substantial amounts of carbohydrate. Some lichens contain cyanobacteria that fix nitrogen, and these have higher protein value, but they are reported to be less favored by some mammalian lichen-eaters. However, mountain goats are known to eat them. The white foam lichen that the goats by Nugget Falls were eating has about seven percent protein, which is not high, but better than many other species.

Goats, deer, moose, and caribou are herbivores with four-compartmented stomachs adapted to help break down the complex carbohydrates that compose the bulk of the lichens and summer herbage that they eat. A well-developed bacterial flora turns the big carbohydrate molecules into simple sugars that can be absorbed in the intestines. Regional differences in the available species of lichens are accompanied by regional differences in the bacterial flora adapted to these dietary differences. A well-adapted bacterial flora can increase digestibility several-fold.

A now-classic story is that of the introduction of reindeer to St. Matthew Island in the Bering Sea. The Coast Guard had a station there and in 1944 brought in twenty-nine reindeer for an emergency food supply. But the Coast Guard departed a few years later, leaving the reindeer. By 1963 the herd had increased to about six thousand animals. But the population crashed, during the next two years, to just forty-two animals. They had eaten up most of the lichens, and an extremely severe winter, with deep snow, high winds, and low temperatures, quickly finished off thousands of them. By the 1980s, not one was left.

Other mammals eat lichens too. In some areas, horsehair lichen (Bryoria), which is often common on tree trunks and branches, along with certain other arboreal lichens, comprised eighty or ninety percent of the diet of flying squirrels. Red-backed voles eat horsehair lichen and reindeer lichens. These rodents do not have the complex stomachs found in deer and goats, but they must have a good community of bacterial to help digest all the lichen that they eat.

Hordes of invertebrates eat lichen too. There are mites, springtails, small insects, snails and slugs that include lichens in their diets. Sometimes one can see the distinctive scrape marks made by snails or slugs that rasped off the surface of flat, leafy lichens.

Humans eat lichens too, but they often boil it in several waters to remove bitter flavors and cook the lichens in various other ways. These treatments probably improve digestibility as well as flavor.

Lichens are known to accumulate pollutants from the air; in fact, some are useful indicators of air pollution because they sicken and die off in filthy air. They also accumulate radioactive fallout. Even low levels of air-borne pollutants and fallout build up in these lichens, and therefore the animals that eat lichens may regularly accumulate lots of pollutants and radioactivity in their bodies. And then the predators of the lichen-eaters get poisoned too: The wolves and humans that eat deer and caribou, the eagles and ravens that scavenge the carcasses, the owls that hunt rodents, the birds that glean small insects…all of them can accumulate damaging material from polluted and radioactive lichens. In some cases, the buildup of dangerous stuff may be sufficient to change their behavior, impair disease resistance, or diminish their ability to reproduce.