December bricolage

A female hairy woodpecker visits my suet feeder regularly, and I’d bet any money that she is the same one that came all summer long, as a juvenile, in the company of a male, presumably her father. She learned well from her dad, and she still comes.

One day in mid-December, I spotted her wrapped around the suet feeder, her tail curved around one end as she pecked away at the other end. A sudden fluttering caught my interest, as another woodpecker landed briefly, to snatch a quick bite. The new arrival stayed just long enough that I could see her small bill and also see that she was much smaller than the hairy woodpecker. So there was no doubt about it; it was a downy woodpecker. I’m told that they seldom nest in our area but we sometimes see them in the off-season.

On a gray and foggy day, I turned on to the road by the Pioneers’ Home, where the line of young cottonwood trees is often used for perches by eagles scrounging from the nearby dump. On this day, half a dozen eagles were hanging out on the cottonwood branches. In the fog, the eagles were black, the graceful branches were black, the whole array artistically displayed like silhouettes on a silvery backdrop. Splendid!

A few days later, I wandered down the east shore of Mendenhall Lake, then cutting over to the Moraine Ecology Trail. Some post-holing, some bush-whacking, a wet foot from finding a soft spot in the ice—but the quietness was pleasing. The sound of Nugget Falls and scattered raindrops tapping on my cap—that was it. Aaah—maybe a red squirrel chattering over in the woods. I found a thriving, bright green patch of stiff clubmoss, poking perkily up out of the snow, still bearing immature cones. Surprisingly, there were no hare tracks, but beavers had been busy in a couple of places, packing down a trail between ponds, dragging a few branches over the snow, and starting new cuts on some big cottonwoods. An ermine had bounded from one clump of brush to another. The only observable activity was provided by two small, flying insects, maybe midges.

Seeing those little fliers reminded me of other ‘bugs’ that come out on the snow, at least on days of mild weather (although some caddisflies spend the whole winter as winged adults). Several kinds of arthropods, from many different taxonomic groups, can be active in winter; here are some of them: a variety of tiny flies known as midges are active in winter; most fly about but others are flightless.  Males of a moth called Bruce’s spanworm fly in late fall and early winter, mating with wingless females that lay their overwintering eggs in protected sites such as bark crevices. There are winter-active craneflies that dance in swarms, mostly in fall and spring but also in winter, and stoneflies that emerge in late winter, crawling onto land to mate. A fungus gnat can tolerate very low temperatures because it has an antifreeze protein in head and thorax (but not the abdomen, which can freeze and apparently thus reduce evaporative water loss). The famous iceworm (it’s really a worm, somewhat related to earthworms) lives on glaciers, crawling down into cracks and crevices where the temperatures are said to stay about thirty-two degrees Fahrenheit; so they don’t freeze and can go on feeding on microscopic algae and detritus.

Springtail. Photo by Bob Armstrong

And then there are the springtails, non-insect arthropods, most of which can hop about using a forked appendage on the abdomen. Several kinds can be found hopping or crawling over the snow, looking for microscopic bits of food or dispersing to new places. Their predators are out too, including spiders, beetle larvae and danceflies (see photos). A study of one kind of dancefly found that males swarmed near selected landmarks on sunny, windless days in winter, at temperatures as low as eight degrees centigrade. The males carried captured insects to lure females to the swarm, presumably eventually using the prey as a courtship gift.

A dance fly with a springtail. Photo by Bob Armstrong

Thanks to Bob Armstrong and John Hudson for guidance about winter arthropods.

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Ice and quiet

One day in early December, a friend and I set out to check part of the West Glacier trail and the route along the lakeshore. It was raining, of course, as it had been for days seemingly on end, but the fierce winds had abated. We thought the several creeks that flow across the beach might be flooding (as lots of other creeks were) and too deep to cross happily with just hiking boots on our feet. But the first couple of creeks were no problem; that was encouraging. We eventually got to a deep, wide creek that was too much for us, so we detoured up to the main trail, crossed a convenient bridge over that stream, and went right back down to the beach.

Walking along the cobbly beach allowed us to have what little light was available on that dark, dismal day. As we approached the north end of the beach, we began to see huge, thick plates of ice stacked up on the shore, perhaps the works of those terrific winds a few days earlier. In some places, the ice plates were stacked up four or five deep.  Some ice plates, maybe shoved by the slabs arriving behind them, had plowed into the gravelly beach, raising a berm about a foot high.

Photo by Kerry Howard

I know nothing about the physics of ice fracturing. Many of the slabs had well-defined corners; only a few were very rounded. It seemed that quite a few of those corners made a nearly perfect ninety-degree angle. That was probably  just a random happening; I’d need a big sample to find out!

Lunchtime at the end of the beach, before straggling up the muddy cut-off trail to the main West Glacier trail. It was very quiet out there—just the roar of Nugget Falls across the lake, the tapping of some rain drops on my cap, and an occasional clunk of one slab of ice lightly hitting another. We talked about what ‘quiet’ means.

Those of us who live in town often think of our places as quiet. There are sounds of traffic on the roads, airplanes overhead, boats on the channels, the garbage truck dumping the trash can, sometimes people talking while passing by, not to mention the ordinary sounds of the fridge or the furnace turning on. We learn to tune out the noises that are familiar and ignore the temporary intrusions. And we call that ‘quiet’.

Although almost no place in the real world is totally silent, I thought it might be interesting to find out what we can hear in places and times when all human-caused noises are absent and no tuning out is needed. Fortunately, here in Juneau, we can find suitable places and times for this exercise rather easily. So I enlisted the aid of a couple of friends to do a little sampling. The ‘game’ was to find a place and time devoid of anthropogenic sounds and then spend four or five minutes just listening. To do this requires some (brief) concentration, allowing no potential mental distractions, such as an eagle flying high overhead or a mink running across a beach or any worries you may have brought with you.  

For the record, here are a few of the listening samples we obtained, in the middle daylight hours, in early winter.

–Eagle Beach: wind rushing through the tops of spruces while lower branches rustle more gently; rain drops plinking on the water surface and thudding on rocks, waves lapping the shore, a raven calling overhead, a red squirrel chattering in the woods.

–Boy Scout beach: distant call of a gull, faint sound of gull wings just offshore, wavelets coming onto the beach.

–Nugget Falls trail: roar of the falls, ravens calling from the slopes of Thunder Mountain, a gull’s call, sound of ice cracking on the lake surface.

–Basin Road: a flock of chickadees conversing in the trees, the creek rippling over rocks, a gentle breeze stirring spruce branches, raindrops on the observer’s hood.

–Auke Rec: surf, wind in the trees, rain hitting the rocks, raven calling, Barrow’s goldeneyes calling.

–Horse Tram Trail meadow (two observers): distant waterfall on Peterson Creek, distant water to north, ravens to west and north, unknown bird near the meadow, a crow, companion dog walking and breathing.

Not very exciting, eh?  It was about as quiet as it can be, out there. That’s part of the point. A poet called such a time of conscious attention an ‘active stillness’. The exercise is a little like a short meditation, with the focus directed outward, but I find that the peaceful effect is internalized—a little relief from other concerns and whatever tensions were building. A moment of calm that, for me, is similar to the peace that comes with some well-loved pieces of classical music, with the addition that there is a feeling of connectedness to the natural world.

It’s not an exercise for everyone, of course. You have to be ready for it.

Early winter walks

A visit to the lower reaches of the Herbert and Eagle rivers usually turns up something of interest. A recent warm spell meant that looking for critter tracks in snow would be a vain endeavor. However, the sands were well-decorated by several animals.

Deer tracks old and new went every-which-way. One trackway went right to the last bit of sand and disappeared, so that deer probably swam the river. Maybe it took advantage of the current to arrive at some point well downstream. There were mink track and a good print of a small otter. Beavers had trekked back and forth over the sand bar, one of them recently toting a twiggy branch that left a well-defined pattern. Local beavers had a big cache of small branches for feeding little, growing beaver-lets through the winter.

Perching on a convenient log and pulling a snack from a backpack had the often-predictable result of attracting a black-feathered opportunist. This raven was obviously an experienced moocher and stood expectantly less than fifteen feet away. So the snack was shared. As experienced as that bird was, it approached tidbits tossed only three feet away with the characteristic sideways hops, ready for a quick dash to safety if needed. Just as the supply of snacks ran out, another raven came in and missed the fun.

The west side of Mendenhall Lake caught the brunt of some very strong winds in early December, piling up big plates of broken ice. I went back out there a week later, when a light snowfall had brightened everything. The ice plates were still there, but this time one of them featured the only wildlife seen on that walk: a caddisfly. One of the big chunks of ice was tilted up, and the critter was walking down the steep edge. As it did, a small bit of ice broke off below its feet—I like to think that the insect kicked it off. Someone said it looks like the critter is climbing down its own Denali.

A winter caddisfly, sometimes called a snow sedge, walks down an icy ridge on the shore of Mendenhall Lake. Photo by Kerry Howard

This caddisfly has a name (probably Psychoglypha subborealis) and a nickname (snow sedge). It is winter-active: both males and females have been found at times of very cold temperatures—as low as minus twenty or thirty degrees Centigrade, having emerged from their freshwater larval stage in the fall. When they emerge, they are adult in form but sexually immature. They mature gradually during winter, using up stored body fat in the process and females developing their eggs. They mate and lay eggs (in open fresh water) in early spring, and then apparently die, after a life span of roughly six months.

This caddisfly is not unique among insects in having a life history involving winter activity, but there are not many spend an entire phase of their life history in winter. I wonder about the ecological pressures that led to the evolution of such an unusual habit. Certain kinds of stoneflies customarily emerge, as adults, from fresh water streams in late winter, as soon as the streams aren’t completely covered with ice. Temperatures are often below freezing, but these winter stoneflies have ways to cope with the cold. They are interested in mating at that time, maybe getting a head start for their larvae in the streams?

On a group hike to Crow Point and Boy Scout beach in mid-December, when there was nice, fresh snow on the ground, I found some mouse tracks, a vole highway between grass clumps and some wanderings, and a set of squirrel tracks. Weasel tracks were all over the place—maybe hunting was not-so-good and lots of searching was needed? Or are there lots of weasels out there? We watched a small black bear cub in the tall grass, where it was digging persistently for some time, apparently finding edible roots. There have been reports of an orphaned cub in this area (and elsewhere), and this one was all alone. However, it seemed to be fending for itself reasonably well, and although it was not very chubby, we hoped it could eventually hibernate successfully.

An orphaned bear cub forages in the meadow near the boyscout camp. Photo by Denise Carroll

Splash power

Some weeks ago, I wrote about spore dispersal in bird’s nest fungi, in which the mature spores are held in a small cup and when a raindrop falls into the cup, the spores are splashed out. I decided to learn more about what other species use raindrops for dispersal. It turns out that raindrops have been put to work, so to speak, to disperse spores, seeds, little asexual propagules, and even sperm.

Splashcups are apparently the most common means of using raindrops. Seed dispersal from splashcups has been reported for many genera of plants, including some that grow in our area: Veronica (brooklime or speedwell), Sedum (stonecrop), Sagina (pearlwort), and Mitella (bishop’s cap). However, I’ve not been able to confirm that our particular species of these genera have this adaptation. Something to look for!

Splashcups for seed dispersal are typically small, just a few millimeters across, and more or less funnel-shaped, with the sides of the funnel not too steep and not too spread out. Small seeds are splashed out at various speeds, up to a meter or so away from the parent plant. Splashcup plants are generally small, herbaceous species; they grow in a variety of habitats.

Some mosses use splashcups too, for dispersal of sperm from male individuals. The raindrops give the sperm a head start on their way to receptive females, but once started, they have to swim to their final destination (thus needing a film of water to complete the journey). The juniper haircap moss (Polytrichum juniperinum) here in Southeast is one of these, and other local haircaps may also do things this way. Other moss genera in Southeast with this adaptation for sperm dispersal include Atricum, Plagiomnium, and Mnium, but again I’ve not succeeded in confirming that our local species do.

Another moss uses splash cups made of modified leaves to disperse ‘gemmae’, which are asexual clusters of cells that can germinate and form new individuals. This moss is called pellucid four-tooth moss (Tetraphis pellucida); it disperses its sexual spores by wind. Although it is found in south-central Alaska, Yukon, and B.C.—that is, all around our area, but there’s apparently only one record, so far, for Southeast (in Sitka).

The lung liverwort (Marchantia polymorpha) occurs all over Southeast and belongs to a genus known for gemmae dispersal by splashcups and raindrops. In addition, males bear their sex organs on little, stalked ‘saucers’ (not the technical term!) and sperm are released onto these saucers. When a raindrop hits the loaded saucer, the sperm can be dispersed as much as sixty centimeters away. Then they have to swim, in a film of water, to a female.

A familiar lichen genus is Cladonia, some of which are known as ‘pixie cups’. These make stalked cups that contain little asexual granules (technically called soredia) composed of bits of fungus and algae that are enough to start a new lichen individual. These tiny granules can be splashed up to a meter away by a raindrop, but they may also travel by wind.

Another type of raindrop-assisted dispersal is thought to occur in Tiarella (foam flower), which we often see here. The seed capsule is shaped like an old-fashioned sugar scoop, with a long lower lip. A rain drop hitting the lower lip could flip out the seeds. This spring-board mechanism is also seen in some club-mosses (Lycopodium, including our local L. selago), which disperse little vegetative, non-sexual propagules (called bulbils) this way.

Fungi have a couple of other unusual ways of using raindrops or at least water drops for dispersal. Some of the puffballs release spores when the tender top of the mushroom is struck by raindrops. Certain fungi (not specified in the available literature) release spores by a water-drop-driven catapult: There is one drop (apparently produced by the fungal spore) at the base of a spore and one (source not given) along the side of the spore. These two drops merge, creating a big enough drop with reduced surface tension so it breaks open, pushing the spore from its attachment and popping it loose.

See this video by Bob Armstrong for an example of fungal dispersal by raindrop.

Raindrops even get involved in pollination of flowering plants. In some buttercups (Ranunculus) and marsh marigolds (Caltha), rain splashes pollen from the anthers (where pollen is produced) to the receptive stigma of the same flower.

All those splashcups and springboards and catapults are evolved adaptations of the respective species. They function to the benefit of the plant or fungus by increasing reproductive success via successful dispersal.

However, raindrops may also have non-adaptive effects, such as transmission of foliar diseases. If a raindrop hits a leaf infected by bacteria, viruses, or fungus, it bounces, potentially carrying the infective agents with it in a water drop. The distance carried depends on many factors, including water-drop size, leaf shape and orientation and its motion when hit by the rain drop, and location of the original infection on the leaf. A complicated matter, indeed, but of some importance especially in agricultural monocultures. 

Armored defenses

Organisms that can’t run away or hide from would-be predators often defend themselves with some sort of armor that deter access to the soft bodies inside. Clams, cockles, and mussels are enclosed in hard shells. Turtles and armadillos wear hard body-armor.  Butternuts and black walnuts are famously tough nuts to crack. In some cases the armor is not a hard shell but a covering of sharp spines. But for every armored defense, there is a counter-measure that allows some predators to get at the edible parts inside.

The sharp teeth of rodents can gnaw a hole in the side of a seed. Years ago, I sometimes used cherry pits as bait in live traps for mice: the mice could neatly carve a hole in the side of that seed and extract the nutritious nugget inside. Fox squirrels in the eastern deciduous forest harvest and cache black walnuts for later consumption, gnawing open the tough shell (note: these are not the domestic thin-shelled “English” or Persian walnuts we buy in the store). Brazil nuts are notoriously hard-shelled, but agoutis can open the big enclosing fruit and extract the very hard seeds, which they cache, to be opened and eaten later.

The strong bill of a blue jay can hammer open an acorn. Oystercatchers sometimes pound on a mussel shell to break it, then sever the shell-closing muscle, allowing the shell to open. However, our black oystercatcher is said to prefer just to jab its long bill into open shells and then sever that muscle.

Hard shells can be smashed by dropping then onto a hard surface. This seems to be a popular method for a variety of predators. Crows and gulls often do this with shellfish—carrying the prey high above a rocky beach and letting it fall, then coming down to extract the flesh from the broken housing. Sometimes it takes several drops. And there’s often a sneaker nearby who’ll try to snatch the meat before the original bird descends. Some gulls are reported to select hard surfaces for dropping big clams but can use softer mudflats for smaller clams.

Several kinds of eagles are said to carry turtles aloft, then letting them fall onto rocks and smash open. New Caledonian crows drop candlenuts onto anvil stones; then they pry out the edible nut. Coconut crabs eat many things, but when a coconut is on the menu, the crab may climb a tree and drop the large nut to crack it, then finishing the job with its big claws.

Sometimes a tool is used as a hammer to open a food item in a hard shell. Chimpanzees (and a few other primates) are well- known for this behavior, teaching the method to their offspring. Sea otters hold a shelled prey on their chests as the float about, using a rock to beat on and crack the shell. Egyptian vultures may crack ostrich eggs by throwing stones at them.

Or maybe you get somebody else to do it for you. There’s the famous situation in Japan, in which carrion crows have learned to exploit traffic patterns to open hard-shelled walnuts. The crows are reported to wait for a traffic-stopping red light and then place walnuts in the roadway before the light turns green. When the traffic moves on again, the vehicles pass over and crack the nuts, and the crows zip down to grab the kernels. They are also said to drop the nuts in front of moving cars. Similar behavior has been reported for American crows in California, except that there the behavior is not timed to the traffic patterns.

Octopuses have at least two means of opening clam or mussel shells. One method is using the suction cups on the arms to pull the two shells apart. Another method is to drill through the shell (octopuses have two kinds of drills for this purpose), sometimes injecting a venom that relaxes the shell-closing muscle. Different kinds of octopuses have their favorite points of where on the shell to drill. Sometimes an octopus uses its beak to chip off thin parts of a shell, giving access for injection of venom.

Whelks are big, carnivorous snails that drill through shells to get at the meat, using the file-like radula. Lots of insects also can drill through hard seed coverings. Weevils provide good examples; the females of one kind of weevil bore into acorns of various species of oak, chewing channels with mouthparts at the end of the long snout. They then lay eggs in the acorn and eventually the larvae feed on the nutritious material inside (which the oaks intended for their seedlings).

Pinching can do the trick too. The big claws on crabs and lobsters can crack the shells of other crabs and some molluscs. The hefty bill of a grosbeak can crack hard seeds and beetle carapaces.

The ultimate insult to armored or spiny defenses might be just ignoring them and swallowing the prey whole. Gulls and crows gulp down small molluscs and cough up the shells later. These birds can also swallow small sea urchins, somehow sliding that spiny body down their gullets (see photo). Hard, prickly sea stars can be crammed down a gull’s gullet too (photo). Ouch?

Photo by Bob Armstrong

Photo by Bob Armstrong

A few vertebrates are defended by armor plates or spines. How do predators deal with these defenses? Armadillos carry a suit of hardened plates, and one kind of armadillo can roll up into an armored ball. How predators gain access to the vulnerable parts isn’t clear—perhaps a cougar or bear just gives the victim a big swat with a paw to tip it over and disorient it, exposing the vulnerable underparts?

When threatened, European hedgehogs roll up into a ball, erecting their spines to present a predator with a spiky mouthful. European badgers can wedge open the spiny ball and get at the tender belly. Foxes eat hedgehogs too, but they are said to be less successful in attempts to disarm them.

The spines of an American porcupine are a formidable defense—the beast turns its back with raised spines, brandishing its spiny tail. Many an ignorant or over-eager dog can attest to its effectiveness. If it can, the porcupine hides its face between tree roots or its paws. For good reason! A fisher commonly attacks a porcupine by grabbing and injuring its unprotected face, then flipping the damaged victim over to attack the belly and kill it. Other carnivores can use these techniques too.

There is no perfect defense.