Small vertebrates in winter

On the last day of November, on the way to the end of the dike trail, I saw a warbler fossicking about on a mossy area near the spruce trees. It was probably finding small moribund insects and spiders. I got a good look at it: a male Wilson’s warbler. That was a surprise! I didn’t expect to see any warbler at that time of year, especially since we were having a series of cold night with temperatures in the teens. I could only hope that he would find enough food to fuel a flight to somewhat warmer places.

Photo by Gus Van Vliet

I began to wonder if this sighting was unusual. So I explored the information recorded in ebird.com a little and found that, over the years, this warbler has been spotted in northern Southeast Alaska uncommonly in November and December and even, but very rarely, in the depths of winter. Then I wanted to learn what other warblers (of those that commonly breed around here) are seen at this time of year. In particular, I thought of orange-crowned warblers and yellow-rumped warblers, which I often see in early spring (March-April), so they seemed like candidates for appearing in early winter too. Although yellow-rumps are recorded quite frequently in November-December and rarely in deep winter, orange-crowns are rare in northern Southeast in November-December. Then I found out that early arrival is not necessarily a good predictor of late fall sightings; Townsend’s warbler comes early but is seldom seen in late fall.

Do the warblers that sometimes stay into late fall have anything in common that might explain their presence? All our warblers feed chiefly on arthropods. Wilson’s, orange-crowns, and yellow-rumps are also known to eat berries and other small fruits at times, but so do some other warblers (but perhaps less often). And, in any case, our region does not offer many small fruits suitable for small birds. Maybe those three just strayed from a relatively nearby wintering ground? But that could not be the case for Wilson’s, which winters in Mexico and the Gulf coast. So neither what we know of diet nor proximity to wintering grounds goes very far to accounting for the three late-stayers. Perhaps they just misread a cue or get delayed by some unknown matter.

Other small birds characteristically spend the winter in Alaska: Pacific wrens, black-capped chickadees in the Interior and the closely related chestnut –backed species here, red-breasted nuthatches, and brown creepers. All of these species usually weigh about the same as the warblers discussed above: in the range of 8-12 g (YRWA at the top of the range). Being small means that they cannot store large quantities of fat to sustain themselves overnight or for several days— their metabolism is quite high and they are so small that there is no place to store a lot of fat on the body as large animals (such as bears and beavers) can do. And they don’t hibernate—they stay active all winter. Some of them (chickadees, nuthatches, occasionally creepers) include seeds in the diet, which are available in winter and which the warblers don’t eat. Chickadees, creepers, and nuthatches often cache their food—in effect, storing their energy outside the body, and black-capped chickadees (possibly also the others) have a temporary increase in brain size, with increased spatial memory during winter.

Red-breasted nuthatch. Photo by Bob Armstrong

In addition, chickadees (the black-capped species has been studied, but other species may do this also) can reduce their metabolism at night and let body temperature decrease; this saves energy, although in extremely cold conditions, it may be impractical, because body temperatures can’t drop too far (being ‘warm-blooded’). The over-wintering species have several tricks that are apparently not used by the warblers. Roosting in cavities, away from the winds, can increase the effective temperature by 25% or more, saving energy, and any sheltered site would be helpful to some degree. Moreover, roosting with companions would also help save energy. Both sheltering and companionship are used by these four species upon occasion. Wrens sometimes roost in cavities, sometimes communally. Chickadees sometimes roost in pairs, sometimes in cavities but more usually in dense foliage. Creepers sometimes roost in small groups, often in sheltered spots. Red-breasted nuthatches may sometimes use cavities, and if seed crops fail, they travel southward in search of better foraging. Apparently none of these methods (except for travelling south) is used by the late-staying warblers (as far as is known).

I can’t resist adding one more bird species: the common redpoll, which is slightly larger than those birds already mentioned, averaging about 13 to 14 g. They eat lots of seeds, especially in winter. And they have the intriguing habit of using snow blankets, dropping down to the snow and making a tunnel with a chamber at the end, 6-11 cm below the snow surface.

Shrews are very small, short-lived mammals that stay active during the winter. They can’t store sufficient body fat, so they have to keep eating every day—twice or three times their body weight in bugs, worms, and other inverts, to maintain their high metabolic rate. European common shrews (Sorex araneus) , weighing less than twelve grams, undergo a marked autumnal reduction in body size, including spine, internal organs, skull, and (!!) brain, as they enter their first winter. Home ranges are smaller and cognitive function related to spatial explorations seems to be diminished in winter. But they regain body mass and re-grow these parts in spring, almost to the original size, ready for the mating season. Researchers suggest that those winter reductions may be a way for saving energy. I have not found comparable information about Sorex species in Alaska, but similar seasonal changes might occur. I wonder what the Alaska tiny shrew does, living in the Interior and weighing less that two grams. Interestingly, the pygmy shrew (in a different genus) does not show these seasonal patterns, leaving open a number of intriguing questions.

European studies of least weasels and stoats (or ermine) have also revealed seasonal changes in depth of the braincase. (Both stoats and least weasels are considerably larger than shrews: stoats weigh up to about 330 g (esp. males), and the weasels weigh up to about 190g, esp. males. However, the long, narrow body shape means heat conservation is difficult, and the metabolic rates are high). Again, brain size reduction may be a way of saving energy. Juveniles decrease braincase depth during their first winter but regain it the next summer. Adults also lose braincase volume in winter and regain it the following summer, but males regain more than females (perhaps related to female’s energy expenditure on rearing offspring and less need to range widely).

Thanks to Gus van Vliet for helpful consultation.

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Bricolage

There were good minus tides in May and June, and I went out with some friends to take a look at the intertidal zone in two places that we’ve checked in previous years. We found lots of small white cucumbers, numerous green sea urchins, and theusual sea stars, but fewer of them—and only one baby king crab, no whelks, few hermit crabs or lined chitons, and so on. In general, the diversity and abundances of intertidal critters seemed low to all of us who had looked there in other years.

Strange things have been and are happening in the regional and local environment. Sometimes devastation of intertidal communities is widespread; for instance, in 2021, high temperatures wiped out invertebrate populations, exposed at low tide, for many miles of coast in southern B. C and northern Washington. But locals surely would have noticed if such a major event had occurred here (although a recent Pacific marine heat wave may have left residual effects in our area). 

Other effects are more localized. Outbreaks of the wasting disease have damaged sea star populations. Heavy rains can overwhelm the local wastewater treatment system, so that ‘dirty’ water enters the marine system. The past winter brought very cold temperatures, big storms, and the risk of wind-chill toexposed intertidal invertebrates. Massive winter snowfall followed by heavy rains and unusually warm temperatures in spring increased freshwater input to coastal waters, and the present summer brought extremely high air temperatures for days at a time. These kinds of extreme conditions probably affected many intertidal animals (and plants). Such effects would probably vary among local areas, depending on exposure to sun and wind and freshwater input, slope of the rocky beaches, among other factors. As a marine biologist commented: things seem to be somewhat out of balance and the consequences are likely to be patchily distributed.

One day in July, I went out (on another good minus tide) to one of the places we visited in May and June, not wanting to believe the impression of a depauperate fauna. I didn’t change my mind on that, but I had one piece of good luck: lying on the mud under a small, flat rock, I found a little fish that was obviously not the usual gunnel or prickleback. It was a graveldiver! It had a long, thin body with a slightly knobby head—looking (as some have said) like a tiny snake; its tan color was distinctive (although some individuals may be darker). I found a good match for this creature in Aaron Baldwin’s on-line field guide(Sea Life of Southeastern Alaska, co-authored by Paul Norwood).

Graveldiver. Photo by Aaron Baldwin

That was exciting! But it seems that very little is known about the biology of these little fish—I reckon that they are hard to study in detail. Some researchers suggest that they may burrow very deeply and carry on their reproductive activities deep in the sediments and gravels. They have tiny, sharp teeth and are presumably predators. 

Bits and pieces from other places: Out at Pt. Louisa, I saw a shrub that looked strangely lacy from a distance. Close up, I could see that it was an alder almost all of whose leaves were severely skeletonized. The agents of defoliation had been chewing all summer, and I found the culprits working away on the few remaining leaves that had green tissue between the veins. They were woolly alder sawflies, a European species that occurs in various parts of North America, including British Columbia and Alaska. Female sawflies lay their eggs near the midrib of the leaf. The larvae are reported to feed first on the upper surface of the leaf and later move to the under-surface. The last larval instar of this species is covered with a white, woolly secretion, giving it its name. They overwinter in cocoons in the soil, emerging as adults next spring.

Woolly alder sawfly larvae

In mid-July, as I walked along the Boy Scout camp trail, I spotted an extremely small shrew, sitting in the middle of the trail, having lunch. I stopped and watched; it calmly nibbled away for a few more seconds and then scooted off the trail. I presume this was a young individual of one of our relatively common species here, which weigh roughly five or six grams as adults; the one I watched was that big. There are, in Alaska, two shrew species that are extremely small: the pygmy shrew, at about three grams (slightly smaller than most of our rufous hummingbirds), and the Alaska tiny shrew, at approximately two grams. But they live Up North and are not recorded from Southeast. (For the record, shrews are too small to store enough fat to overwinter, and they stay active all winter long, looking for food, burrowing through the snows.)

In Haines, there is time between ferry arrival and departure (after the loop up to Skagway and back) to take the convenient Haines Shuttle out to the Battery Point trailhead for a short walk; walking on conifer needles instead of roots and rocks was a treat. Baneberries were ripe; the common color is bright red, but there were two plants with white berries, an uncommonmutant form. Partway along that trail is Kelgaya Point, a lovely, rocky headland with a variety of micro habitats for plants. In late July, numerous small iris plants showed no evidence of having flowered, with one lone exception. A ground-covering mat of crowberry, which we more usually see at mid-elevations, had apparently produced no fruit at all. The flower show was provided by spectacular stands of yellow paintbrush and blue harebells.

Tracks in December

A warm, very wet spell in early December made the lichens and mosses all perky and colorful. Beavers left their distinctive foot marks in a thin dusting of snow and swam out around their winter caches of twigs, tail-slapping when we passed by. In a ‘real’ winter, they would be tucked up into their lodges, snoozing a lot, talking quietly with their offspring, and occasionally nibbling a twig from the cache. The kits of the year, however, would be chewing twigs all winter long, as they continue to grow. Bears were out and about too, mom and cub leaving their tracks near Dredge Lake, instead of entering into serious hibernation. That entails a profound reduction of metabolic rate, shutting down digestive processes, and very little activity inside the den, quite a contrast with beavers.

Then, in mid-December came a lovely and welcome snowfall, just a few inches at sea level. It wouldn’t last, of course, in this time of warming climate, so I dug up my snowshoes and headed to Eaglecrest. There the snow was maybe a foot or so deep and just right for poking around on a day when the lifts weren’t running. Snow was falling thick and fast, quickly covering any little tracks of mouse or shrew. But under the trees were prints of snowshoe hares. A small-footed canine creature had run across a wide open area, leaving a long, straight line of well-spaced prints. There was no evidence of any human anywhere nearby, so I guessed that a coyote had raced along. But very few critters made themselves visible—a porcupine that seemed to think that if it could not see me, then I could not see it; and one flying insect, probably a stonefly. Nary a bird to be heard or seen not even a hopeful, attendant raven.

A couple of days later, a nice little cold snap meant that even at sea level, there remained a few inches of snow cover. I went out the road to some meadows, where I plonked along on snowshoes—a convenient way to deal with snowy humps of frozen grass. Oddly, there were no shrew tunnels to be seen, nor any squirrel tracks, and again not a bird could be found.

But otters had been quite busy. They had fossicked along a tiny rivulet, trampling some spots quite flat; there were more than one of them, apparently, so perhaps a family of mom and well-grown pups. I lost their trail when it went under the trees where there was no snow. However, a few minutes later, I encountered their characteristic slide marks where they had crossed a snowy, open area, pushing off strongly with the hind legs and gliding smoothly even over flat ground. This is probably more fun than stomping around on snowshoes! A bit farther on, otters had come up out of a tiny stream and snuffled all around the nearly buried ends of several low, trailing spruce branches. What was going on there, I wonder.

Some days later, I looked for tracks in another meadow out the road, but there had been little recent activity. A couple of squirrels had explored the meadow edges, out of the trees and back again, diving under humps of bent-over grasses. Before the last little snowfall, porcupines had trundled over the meadow in several places, on their usual meanderings. They seem to travel quite extensively, perhaps in search of just the right twig to nibble (?). Along a small creek, some critter had burrowed into the bank in several spots—possibly an otter.

Surprisingly, there were no little shrew-size grooves on the surface of the snow, no tiny holes where a shrew dove under the white blanket. Yet this was a meadow that, in previous years, had been laced with trackways of shrews. One shrew had even taken a dive off a vertical mudbank and gone skittering over a gravel bar in a creek. But where are all those shrews now?

A fluttering on the creek-bank caught my eye and eventually turned into a dipper. This bird was foraging along the water’s edge but apparently found little of interest, because it soon took off, upstream. That was the only living animal to be seen, except for one red squirrel crossing the creek on a broken-branch bridge.

Later that day, on another stream, I checked a long-occupied beaver lodge. There were no signs of recent beaver activity here, although the lodge may be currently occupied. However, other woodland folks were interested in the place: porcupines and mink had visited on more than one occasion in recent days. Was this perhaps a multi-species condo? It wouldn’t be the first time that happened.

The slanting light of midwinter that stabs one blindingly in the eye at certain times of day on Egan Drive, did some beautiful things out by the meadows. Some conifer-clad hilltops were brilliantly lit, contrasting with darker slopes below. Light mists collected in the valleys caught the light rays and turned golden. Overhead, some dark clouds gathered amid some white fluffy ones, but bright rays came through the many unclouded areas, where blue sky was a cheery sight.

Snowy tracks

Snowshoes crunched over deep snow. The sky was cerulean blue and the sun gradually crept around the mountain peaks. These were fine days to be out, seeing what we could see. We were especially interested in the tracks left by the wild critters as they went about their daily lives.

–A shrew left a long line of tiny marks by the side of a beaver pond. Short digressions led to tufts of grass or a buried stick, where spiders and bugs, slowed by the cold temperatures, might be found. Shrews only weigh a few grams and have a very high metabolic rate, so they have to eat almost continually. We often see their trails running over the snow and plunging into miniscule holes that lead under the snow blanket where prey might be found.

–Mouse trails are much less common. But one day we found a line of hopping prints that went out of the forest and across the upper intertidal zone to the most recent wrack line. The piles of tumbled rockweed might harbor small crustaceans, wayward seeds, or lost insects—all suitable for a snack. Another line of tracks went straight back into the shelter of the forest.

–Snowshoe hares had been busy in some areas. They too were looking for food, maybe willow or blueberry buds. But occasionally there were heavily trampled spots, very localized, as if there had been a dance or other social encounter. Popular routes became hare highways, packed flat along a small ridge or between two dense spruce stands.

–An otter had cruised for hundreds of yards along a frozen slough, making side excursions to visit (briefly) several beaver lodges. The deep trough left by its passage seldom came out in the open but usually stayed under the fringing conifers. Reaching the shore of a well-frozen lake, the otter abruptly turned around and went back the way it had come. The only open water on its route was a very small runnel below a beaver dam—a place not likely to hold good otter food.

–Across some thin pond ice, a great blue heron had gingerly minced its way from one patch of open water, at the inlet, to another, at the outlet. Taking very short strides on its long thin toes, it seemed to have been treading carefully. Little sticklebacks and juvenile coho, beware.

–In several places, we spotted narrow grooves on the snow surface, where a slim body had propelled itself on small feet. These wandering trails led to grassy tussocks, dove under logs, circled a pile of branches, disappeared under the snow and came out again. A mighty hunter was at work: a short-tailed weasel or ermine, whose coat turns white in winter, except for the tip of the tail. The short-legged, long body of a weasel is well-adapted for diving down vole tunnels and other tight places. However, that body form means that a weasel can’t afford to put on heavy layers of fat; the belly would drag when the weasel tried to run—not good for a hunter that has to keep moving for much of the day in search of prey. In addition to their small size, the body shape of weasels gives them a lot of surface area (where heat is lost) compared to the body volume (muscles and organs that generate heat), so they have a high metabolic rate to keep themselves warm. And that means they have to eat a lot. They eat mice and voles and small birds, and carrion when it’s available.

–Porcupines seem to wander widely, and we’ve found their trails in many places, often still distinguishable under a layer of new snow. One day we found a very fresh trail of footprints and even some quill-drag; we followed it along a little dirt bank until it disappeared over the edge. Looking down, we saw that a small log, sticking out parallel to the bank, had been wiped clean of new snow by the animal’s passage; the trail ended near the end of the log. Of course, we went around to an easier place to climb down the bank and investigated the trail’s end. There we found a deep burrow, with hairs and a few dried-up fecal pellets and a good barn-y smell, that ran into the bank for over two yards: a snug, dry den that had been used repeatedly for some time. Upon close inspection, that little access log had thousands of scratches, evidence of many balancing acts as the porcupine had ventured out and back.

February notes

For lovers of good winter weather, February has been a difficult month, so far: Ridiculously mild temperatures, way too much rain, feeble ice, much too little good snow. Nevertheless, there have been some items of interest.

A Parks and Rec group charged on snowshoes up to Naked Man Lake, below the crest of Mt Troy on Douglas one day. We made a nice trail for some later-rising skiers, who headed up Troy itself and gave us a show as they swooped down. A couple of us weren’t quite up to charging uphill at the pace-setters rate, so we peeled off from the main group at a spot with a good overlook of part of Juneau. We perched in the snow for lunch and were entertained by a shrew, dashing madly over the top of the snow from one tree-well to another. Was it finding food there? Why was it running around in such exposed areas, instead of tunneling more safely under the snow?

On the way down, we noted a small spruce tree, maybe twenty feet tall, that had been totally de-barked. The entire trunk and the bases of all the branches were denuded. That must have been a particularly tasty tree or a desperate porcupine at work. I often see evidence of porcupines eating hemlock bark and spruce needles, but I don’t often see spruce bark as part of the diet.

On the Crow Hill Road on the way to up the Treadwell Ditch, we found numerous worms, very much alive, in and on the ice. They were small, only one or two inches long, and looked, to our ignorant eyes, like baby earthworms. Really? What was going on here? The Pacific Northwest is home to the famous glacier ice worms (related to earthworms), but those supposedly live only on our glaciers.

Some other folks had the good luck to find an unusual fish washed up on a local beach. This turned out to be a ragfish, which have been reported occasionally from other beaches in Southeast. Also, the remnants of one were salvaged from a sea lion near Outer Point. Ragfish live in the North Pacific, mostly in deep water apparently, and do not have a swim bladder, an organ that usually functions to adjust buoyancy. So what are these doing anywhere near the beaches? One researchers suggests that they may be brought by currents into shallower waters or are drawn to productive upwellings near shores.

Ragfish and friend. Photo by Bob Armstrong

Ragfish are very distantly related to perch and bass, but they are characterized by a skeleton that is mostly cartilage and flabby flesh. Juveniles look quite different from adults in body shape and fin shape, and adults have no body scales. A strange creature!

The biology of ragfish is poorly known. Females get to be larger than males, achieving lengths over two meters. They are thought to spawn at depths of two hundred meters or more, laying hundreds of thousands of small eggs at a time. Although the teeth are tiny, ragfish are predators of other fishes, squid, and jellyfish. In turn, they are preyed upon by sperm whales, sea lions, and tuna, and no doubt many others.

Little winter puzzles

Early winter walks yielded some small puzzles for curious naturalists to contemplate. Here are a few of them.

Out at Eagle Beach, on a low tide, we observed many crows, mostly foraging busily. Along the tideline, they forage singly, each one slowly walking along the edge of the water, pecking at this and that, and occasionally winkling out something edible.

On top of the sandy berms lay a cap of fluffy snow, much marked by gull feet and the remains of the gulls’ dinners. On the ends of two of these berms, we saw tight clusters of crows, heads down, poking their beaks at something on the snow surface. When we went to inspect more closely, we found that blackish piles of shell fragments, regurgitated by the gulls, had been scattered as the crows sorted through the pile for bits the gulls might have missed. And most of the excreted yellowish splats of digested gull meals were missing their typical lump of solid waste. It seems that the crows had been dining on gull poop.

That seemed a bit strange, with all the small, intertidal animals that would be expected nearby. But the real puzzle was why the crows did this scavenging of gull ejects in gangs. The snowy berms were covered with evidence of gull presence, but the foraging gangs invariably gathered at one end of the berm, leaving the rest unscavenged. What’s the reason for these poop parties?

In a lovely muskeg we found a long trackway of a shrew. It had meandered for many yards on top of the snow, occasionally diving straight down and re-emerging from the same hole. Presumably it had sniffed out something potentially edible to fuel its constant search for more food. But why hunt on the surface of the snow, where the exposed position sees likely to increase the risk of predation?

Later, On Moose Lake, we found another long shrew trackway, extending for over a hundred yards over the snow-covered ice. This shrew periodically dove beneath the surface and came up a few inches farther on. Again, the shrew was travelling in a very exposed situation, and we wondered what made the risk worthwhile—perhaps a frozen insect or two, or some wind-wafted seeds, but what a dangerous place to look for them.

Plonking around on snowshoes in a muskeg, we noticed a small area in which several tiny shore pines had been mauled. The trees barely stuck up above the snow, but each of them had bent and broken twigs with abraded bark and one or two twigs from which the bark had been delicately peeled. No animal tracks were discernible near these mutilated tree-lets. Who was the culprit? ?A vole that tunneled up from under the snow??

That low-elevation muskeg on Douglas was quite familiar territory for me, but my companions wanted to go to the next higher one. So we thrashed through the blueberry tangles and wind-throws for a time that seemed longer than it really was. We didn’t find much sign of animal activity, but on our way back down, we noticed a huge, rounded boulder near the edge of the muskeg. It was snow-capped, but the sides were covered thickly with lichens, so it had been there a good while. We did a mental double-take and realized that we ‘never’ see boulders in muskegs. But why not? If we assume that trolls don’t make a habit of removing them, then what? The glaciers often left erratic boulders, but why don’t we see more of them in muskegs? Does the muskeg (technically a bog) just cover them up eventually? Then why is this boulder on the surface? Is there a rocky outcrop beneath it? I bet some scientist in Juneau can explain this!

Auk Nu in the deep freeze

As we drove to the trailhead, a full moon still hung in the sky. The temperature was a balmy twenty-three degrees or so, just a day after I registered minus six during the night at my house.

Those crispy temperatures meant that the trail was in the best condition we’d ever seen!

The numerous mudholes were frozen solid, most of the tree roots were buried, and the snow on the board walks was firm. There had been quite a lot of foot traffic on the trail in the days before our walk, so the trail was well-packed with crunchy snow but not icy. We never had it so good!

Hordes of pine siskins pried into spruce cones, chattering all the while, and swarmed from tree to tree. A dark mystery bird sat for several minutes in the top of a spruce, poking carefully at something in the uppermost whorl of branches. If I had to guess, I’d say it could be a pine grosbeak, but it flew off before I could make out any color or pattern.

Lunch in the John Muir cabin was a relaxed but quick affair. It was one of the shortest days of the year, so there was little time for dawdling. The view from the cabin windows was familiar but still spectacular—over the snowy meadows to the channels, where dark islands set in a bronzy sea.

The previous day I had prowled around some of the ponds in the Dredge Lake area. The recent cold temperatures had kept the soft snow in prime condition for checking animal tracks. Snowshoe hares must have been having a party—their tracks were everywhere, sometimes creating a hare highway from one thicket to the next. The tips of small willows showed signs of nibbling.

Mice had been more active than they were on the day just after the snowfall. Their delicate traceries ran from log to stump, or branch pile to grass tuft. I find these trails very beautiful. A shrew trail, even smaller than that of a mouse, ran from one tiny hole in the snow to another. These holes are only about the size of a dime. And in soft snow, the stubby-legged shrews often plow a wee furrow in the surface, as they make their way to a hole. There were tracks of squirrel, a porcupine, maybe a marten, and several weasels that zigzagged among prospective mouse or squirrel holes. Dog tracks were numerous, of course, but I found one set of canine tracks that could have been a coyote.

In the open areas, hoar frost had accumulated on the snow-laden shrubs. Some twigs were encased in a load of white that must have been five inches in diameter. Frost flowers had grown in dense gardens wherever snow did not cover the ice on the ponds; many of the crystals were at least two inches tall and almost as broad. Hoar frost clung to old footprints and ski marks, almost filling the depressions. All the frost and snow on everything certainly makes the short days brighter!

First snows

One of my favorite activities in winter is to go out looking for animal tracks in the snow. In early-mid November this year, the snow was perfect: not a lot of it, but soft enough to register animal passage and firm enough to hold the tracks’ shapes.

So, off to Eaglecrest I went, with two good friends who like these little explorations too. We found lots to look at. Porcupines had plodded in and out among the trees, in some cases making small highways of repeated use. A few red squirrels had ventured out of their burrows. A weasel had covered a lot of ground, bounding with shorter leaps when it went uphill. It investigated many a fallen log and stump in hopes of nice lunch. Weasels have to eat a lot, just to keep warm and feed their active metabolism.

Voles (or maybe mice – it’s often hard to tell which) had run over the snow from one grass tussock to another or from log to bush and back again. These were the most common tracks, often right out in the open meadows, where they might be easy marks for predators. But we saw no signs of lethal events.

Near the road, we found a spot where an indisputable mouse had hopped across. On either side of its trackway were marks of a tail flick. It couldn’t have been a vole, whose tails are very short, so it had to be a mouse. Why it had flipped its tail from side to side was not clear, however; we speculated that perhaps it was slightly off balance on the coarse cobbles at the edge of the road and used its tail to restore an even keel.

Photo by Katherine Hocker

We found a few lines of tiny tracks that were made by shrews. Emerging from one dime-sized hole, crossing over the snow to an equally minuscule hole, occasionally they tunneled just barely below the snow surface.

 

Every so often, we looked up instead of down and noted that quite a few trees had long-dead tops. No mystery there, given the howling gales that sometimes whip through this area. But none of the lower, lateral branches had grown upward to replace the missing tops. We’ve all seen conifers whose original ‘leader’ at the top of the tree has been killed but a lateral branch just below it has taken over as leader, creating a kink in the trunk. We puzzled over why this hadn’t happened on the trees in which the entire top was dead.

 

An answer might lie in the way that hormones control growth. Normally, the leader at the top of a conifer suppresses the growth of lower branches; this is known as apical dominance. But the effects of apical dominance diminish as the distance from the leader increases. So, perhaps, when the entire top of a tree is killed, the distance from the leader was so great that there was no dominance exerted on the remaining branches. Thus, the lower branches had not been suppressed and they did not respond to the loss of the tree top.

 

A few days later I walked out into the Mendenhall Glacier Recreation Area near Crystal Lake. Tracking was still good and there had been lots of activity. A porcupine had trundled across the ice on the lake, and a weasel (I think) had walked (not bounded) along the footpath. Squirrels and snowshoe hares had crossed the path.

 

The most interesting marks were made by a bird, whose wingspan exceeded five feet—surely an eagle. Its wing tips brushed the snow in several places around a patch where the snow had been disturbed. Here I could see some heavy-duty bird tracks, confirming the presences of an eagle. All around this area were raven tracks too. But there was no clue about what the eagle was after—unless it might have been a raven (eagles do capture ravens sometimes). It seemed unusual for an eagle to be hunting in a wooded area where the only open ground, where an eagle could spread its wings, was the path itself.

 

Lots of stories in the snow, so winter was off to a good start for me!

Streamsides in winter

I take a walk on one of Juneau’s many trails almost every day, alone or with friends. Sometimes it’s a bit hard to get myself out the door, because there’s a deluge or big wind, or I’m just feeling lazy. So I remind myself that sitting inside my house practically guarantees that I won’t see much of interest—so get out there and look around, something may turn up. And something always does.

Here’s a sampling of small pleasures that turned up along Juneau streams in January:

–Fish Creek: Huge, thick plates of ice had washed far over low banks on the small, upstream floodplain and into the forest, and also into the meadows around the combat-fishing pond. It was fun to speculate what it would have been like to actually see the ice cakes pushed out of the creek and into the forest (from a safe distance, of course).

–Eagle River: A dipper was foraging along the edge of the river, occasionally disappearing under the ledges of ice that lined the shores. It searched diligently in the riffles and sometimes brought up something that required some work before swallowing—maybe extracting a caddisfly larva from its case.

–Mendenhall River: I checked out the ‘gooseneck’ peninsula where a breakthrough seems imminent. The narrow neck of land is thinner every time I look, and it seems as if one more good jökulhlaup might be enough to make an island of the peninsula tip. I have to guess that hydrologists have determined the large buildings just downstream to be safe from such events.

–Fish Creek: Winter-active beavers had dragged brush from recent cuttings over to their home pond, leaving trails in the old snow. These beavers, and others in Juneau, have obviously not read the books that report beavers holing up in their lodges for the winter.

–Mendenhall River: A pair of hooded mergansers, the snazzy, gorgeous male with a more-demurely -plumaged female, sailed sedately downstream. Hooded mergansers are the smallest of the mergansers; they eat a more varied diet that includes not only fish but also lots of invertebrates. Males and females commonly pair up in late fall and hang out together through the winter until nesting time in spring. Then the female choses a nesting cavity in a tree or nest box, usually not too far from water, lays her fertilized eggs, and incubates the clutch of eggs, while the male, having done his studly task, goes off and leaves her to do the work. When the eggs hatch, the tiny ducklings almost immediately jump out of the nest cavity, fluttering down to land with a little bounce, and follow mama to feeding areas. This species nests in some places in Southeast, but not commonly. In winter, it favors coastal waters such as shallow bays, estuaries, and tidal rivers, so we see it occasionally.

Photo by Bob Armstrong

–Eagle River: Small insects were flying, possibly midges, looking rather like miniature mosquitoes. Some other insects, such as certain stoneflies, regularly fly in winter, but I’d like to know more about midges (if that’s what they were).

–Cowee Creek: A kingfisher winged upstream and perched over a pool. I hoped to see it catch a fish, but apparently it saw nothing worth pursuing. Kingfishers and many other birds have two small areas, called fovea, on the retina of the eye (humans have just one); foveas have a high density of visual cells and provide good acuity. One fovea, near the bill, is used for monocular, sideways vision; this fovea has especially numerous visual cells and is used for finding prey (as well as keeping track of other birds and predators). When a kingfisher dives and enters the water, its vision switches from that fovea to the other one, located away from the bill; using these lateral fovea in both eyes gives the kingfisher binocular vision and better depth perception as it gets close to an elusive small fish that may try to dart away. When the bird dives, its eyes are protected by a nictitating membrane. As some of us have found out when we try to grab something underwater, refraction often causes us to misjudge the depth of that object; kingfishers can avoid much of that problem by diving vertically after prey that is deeper than a couple of inches.

Kingfishers nest in burrows alongside or at least near streams. I have found nest burrows by several Juneau streams. The lower Mendenhall River and Cowee Creek, where it flows through the meadows, have cut steep mud banks that are perfect places for kingfisher nests. But there’s a problem: in both areas the streams are rapidly eroding those banks; what remains is still potentially suitable for nest burrows, but the stability of the banks is obviously uncertain, and high water in spring and summer could wipe out a kingfisher nest.

–Peterson Creek: A little light snow had fallen on top of old, crusty snow. Shrews had traveled far and wide over the top of the snow. One shrew had plunged, presumably deliberately, over a small mud cliff at the edge of the stream. A few feet downstream, its tracks continued on a flat shelf of shore-bound ice. It sure looked like the critter swam from the base of the cliff to the ice. There is a shrew that is adapted for swimming, but it is not as common here as ordinary shrews, which apparently can swim if necessary.

What did I get out of those little walks? Some really fresh air (Juneau is good for that!), mild exercise (followed by a comfy cup of tea), sometimes companionship, sometimes a solitary meditation, and some observations to think about. Not bad for a small investment.