Late September notes

quiet trails, fall colors, and dragonfly migration

It’s been rather quiet along the trails in late September: here a pair of hermit thrushes, there a trio of varied thrushes, and a stray robin or two. Coho were milling about in Mendenhall Lake, rumpling the water surface. From the beach on the west side, I watched a seal or two making bigger rumples as they tried to grab a fish. I saw no coho going up the west-side streams, as they usually do, but they were going up Dredge Creek on the other side of the lake.

I met a dog-walking fellow who remarked on his enjoyment of the fall colors, as we looked at the golden cottonwoods, yellow willow leaves, and the red/pink/yellow leaves of highbush cranberry. Dwarf dogwood has been spectacularly red along some trails, with small spots of color from trailing raspberry and nagoons. Along the lakeshore trail, new willow-roses were developing, showing brilliant red on a background of still-mostly-green willow leaves. The midge larvae inside will emerge next spring, having fed on the inside of the gall, and face the world as adults.

Willow “rose” midge gall

Meanwhile, I was sent a link to an article in a Wisconsin newspaper about huge swarms of dragonflies headed south on their fall migration. Tens and maybe hundreds of thousands of dragonflies were on their way, attracting so much public attention that they even made it into the newspaper (and there are other migrating swarms, on the east coast, near the west coast, and in between). Several species had joined the swarm, but the great majority of them were green darners (Anax junius)—possibly my favorite dragon, very snazzy. The Latin name means June king—“king” perhaps because of its large size, with a wingspan of almost twelve centimeters, bigger than most other North American dragons. They typically breed in quiet waters of vernal pools and marshes, where the females lay their eggs on aquatic plants. These mighty predators are able to capture and eat other adult dragonflies, as well as many other insects. They range over most of North America, coast to coast, from southern Canada to Mexico, Hawaii, and beyond. They don’t get to Alaska except by accident of vagrant winds. But their regular migrations take them from the northern part of the range to the southern part in fall, and back again in spring.

Green darners are well-known for making long-distance migrations and we now know a little more about their fall travels. The advent of miniature radio transmitters, small enough to be glued onto a dragon’s back, allowed researchers to follow their progress for several days. The dragons made an average of about twelve kilometers per day, with stopover days for foraging in between the flight days. They took advantage of northerly winds, after a cool night or two, and typically flew with the wind, although they seldom flew on very windy days.

The swarms are apparently more common in fall than in spring. Swarms are composed of individuals from widespread areas, gathered together in fall to follow shorelines, ridgelines, and other landmarks. Individual dragons bore natural markers in the form of isotopes that could be identified to their approximate sources; natural isotopes of hydrogen, for instance, can have one, two, or three neutrons, changing their atomic mass (‘weight’). The proportion of hydrogen isotopes (in water, for example) varies geographically (e.g., latitudinally), and this is reflected in the body composition of the critters that grew up in different areas.

A simple version of green darner migration divides things into three generations. Generation #1 emerges in the south in February to May, flies north, where it breeds and dies. Generation #2 emerges from that breeding activity in the north, flies south to breed and die. Generation #3 are the offspring of fall migrants and do not migrate; these residents breed and die in the south and their offspring migrate north in spring.

But it’s not really quite that simple! Individuals in the green darner population of some places (data from two studies in the north) seem to be comprised of individuals with two different migratory patterns. A given population may have some adults emerging and breeding in summer, whose slowly growing larvae overwinter in the breeding pond, emerging the next summer to breed there as adults. Other individuals in the same pond are small larvae in early summer (whose parents were spring migrants); these grow quickly, with adults emerging and breeding in late summer and fall, and then disappearing on fall migration. This makes it seem that these northern populations contain both residents and migrants.

Studies of the population genetics have shown that green darners have not differentiated into distinguishable populations but rather exhibit widespread similarities, which indicates genetic mixing throughout the whole population. Spring migrants probably do not go back to where the previous generation of their parental lineage came from; they may settle to breed somewhere along the way. Their offspring therefore cannot be closely adapted to particular rearing conditions in various geographic areas. So researchers now consider the possibility that the life-history differences (resident vs migrant) may be flexible. Perhaps the early larvae decide which life history to take on the basis of some environmental trigger.

There is much to be learned about migratory strategies in green darners. What cues do the migrants use for orientation on the long flights? How do they decide where to settle and breed? Do the offspring of a given female actually embark on differing life histories, depending on circumstances? If life histories are flexible, what are the triggers that determine which alternative prevails? Will the relative frequencies of the two pathways change as the climate changes?


Bright spots

after a soggy summer

The autumn equinox is past, and the days are rapidly getting shorter. It was an exceptionally rainy summer and we can’t expect fall to be much different. Sigh. But there have been some bright spots along the trails in forest and meadow.

One happy sighting in a meadow on the Peterson Lake trail was a bird busily foraging in the mosses, but it was partly obscured by clumps of taller vegetation. All I could see was a brown back and bits of moss flying every which way. I watched for a few minutes, but the flurry of flying moss continued without revealing the forager. So I slowly crept in a circular path to get a different perspective and eventually won a quick side view of the bird’s head. Ah…a red mark on the face and maybe a dark spot on the chest. Then the bird took off, exposing a big white rump patch (but not the colored underwings). OK, of course! A northern flicker, a woodpecker known to forage often on the ground. They nest here occasionally, but I’ve only seen them in Southeast once before this.

A female flicker peers from her nest cavity on Douglas. Photo by Bob Armstrong
This male flicker has the red face mark of the western form and the red nape mark of the eastern form, so it may be an intergrade. Photo by Bob Armstrong

Another enjoyable sighting occurred near the Spaulding Meadows trailhead. A brown creeper zipped across the trail, landed on a tree trunk, and hopped its way up, using its tail as a brace in proper creeper fashion. It was soon followed by another one, which also landed on a tree trunk. But this one quickly moved onto the underside of a branch and hitched its way along, upside down, using just its sharp little claws. It seemed to be quite comfortable in that position and put on a nice little show of its expertise.

We don’t have to go to Vermont or Wisconsin to see good fall colors, even though we don’t have the great stands of oaks and maples. Our colors tend to come in smaller patches, but they offer their own visual treats. A band of cottonwoods on the far shore of Herbert River somehow managed to glow in yellow and gold above a swirl of river mist, despite a steady rain. Willows often turn yellow, but some bear vivid displays of orange and red (why??). The multi-colored leaves of highbush cranberry can be yellow, pink, bright red, crimson, or combinations of those. On the forest floor, bunchberry leaves make carpets in shades of yellow, orange, and red. I also enjoy the pale yellow tapestries of enchanter’s nightshade leaves that call attention to this tiny plant. Still smaller but eye-pleasing are the several kinds of red berries—devil’s club, bunchberry, red huckleberry, bog cranberry, and best of all, the translucent, almost-glowing highbush cranberry. These ‘little points of bright’ matter!

Not to be ignored are the woolly-bear caterpillars, the larvae of the spotted tussock moth. As they grew, they passed through several molts and changes of appearance, and the last instar has the familiar black bands on front and rear with a yellow or orange band in the middle, with some long white tufts. They eat leaves of deciduous trees, but in fall we see them crawling around, looking for a place to build a cocoon and spend the winter.

Fall rains also liven up the lichens and mosses, which are looking quite happy. Fall-fruiting fungi appear—including some showy white ones with a vase-like cap (since I’m a ‘fungignoramus’, I won’t attempt to provide a name).  

The Herbert River trail has always seemed rather dull (until you get close to the glacier area)—lots of the same thing for a long way. But that is unfair! There are actually zones of changing vegetation as one goes up the trail, quite noticeable when I pay attention.  And recently I found several colonies of what turns out to be a common species called the stiff clubmoss, bearing its cones on the tips of the twigs—and thus easily distinguishable from the running clubmoss, with cones on long stalks. How I managed miss the stiff clubmoss all these years, I don’t know, but now that I’ve learned it, I have discovered it in other places too.

For a curious naturalist, sometimes a bright spot (of a sort) comes in the form of a mystery. Along the lower part of Eagle River, a little above its junction with the Herbert, I noticed an odd collection of animal scat. There were maybe fifteen deposits, all within about two meters of each other. They had a variety of sizes and shapes, from cylindrical to lumpy, and all were black. Bears would seem to be the most likely perpetrators. But why so many scats in one place? Bears just defecate where they happen to be and don’t—as far as is known to several wildlife biologists—make communal latrines. One suggestion is that a family of bears had a secure resting place somewhere nearby and used that place for an extended time. But does that account for the very localized deposits? The mystery remains.

September leaf colors

bright highlights in an evergreen landscape

Photo by Bob Armstrong

Juneau ‘leaf-peepers’ don’t have to travel to the upper Midwest or New England for a view of lovely fall colors. This fall there is a pretty good show right here. Although the somber greens of the conifers dominate the landscape, a good color spectrum from yellow to orange to red and pink and even purple can easily be seen.

Returning to the Valley from a hike out the road on a drizzly day when the clouds sat low on top of Benjamin Island, I saw several places along the highway where the golden-yellow leaves of cottonwood seemed to light up the whole area. Patches of fireweed provided flaming scarlet mixed with other shades of red. Across the highway from the Methodist camp, the roadside shrubs and small trees made a splendid pastel expanse of glowing yellows and pinks. Dogwood shrubs sometimes offered a spectacular array of reds and the broad yellow and gold leaves of devil’s club brighten the understory. Highbush cranberry can do it all–yellow, orange, bright red, pink—sometimes even on a single leaf. Closer to the ground, dwarf dogwood and low-bush blueberries do the reds and purples.

The visual color show happens when the leaves of deciduous plants senesce (deteriorate with age) in the fall. The vascular connection between leaf and stem is gradually closed, shutting off the supply of water and nutrients to the leaf and slowing the passage of materials from the leaf to the rest of the plant. Photosynthesis slows and the green pigment (chlorophyll) that does the work of making carbon dioxide and water into carbohydrates breaks down. As it breaks down, leaves lose the green color and the yellow and orange pigments are exposed; they were there all along, capturing light energy and passing it on to chlorophyll for photosynthesis. Chlorophyll is broken down by complex processes that are still being elucidated, but apparently some of the break-down products are still photo-reactive and perhaps potentially damaging, unless quickly de-activated or protected in some way. Meanwhile, the plant retrieves any remaining carbohydrates and nitrogen-containing products of breakdown before the vascular connection closes completely and the leaf drops.

What about the red colors in fall foliage? In most plants, they come from anthocyanins, synthesized toward the end of the season during leaf senescence, using some of the carbohydrates made by the leaf. Anthocyanins account for the reds, pinks, and purples—the hue depending on acidity within the leaf, which depends, in turn, at least partly on the accumulation of carbon dioxide in the leaf when photosynthesis is slowed. It is thought that warm sunny days and cool nights in fall favor the development of red foliage, so our unusually nice September weather might have contributed to the color show this year. I think we can see this effect sometimes in a single highbush cranberry shrub: the side of the bush exposed to light and dropping temperatures at the edge of the woods can be far more colorful than the other side of the same bush that is more protected under the tree canopy.

The functions of anthocyanins have been a subject of much discussion in the literature, but it appears that in autumn leaves they may have a protective function, defending the last days of photosynthesis and protecting from the possibly unstable, over-reactive products of chlorophyll breakdown from too much sun. There may be other physiological functions as well, still to be described.

Many questions remain. For instance: Why do some plants produce only yellow autumn leaves and not red ones? Do they have some other way of accomplishing whatever the anthocyanins do? An interesting comparison comes from quaking aspen, a relative of cottonwoods, in which some clones do make red or orange leaves. Also, willows usually make yellow leaves, but occasional some willow trees make lots of red leaves. Do they all have that capacity but just aren’t triggered to make red, or do only some willow trees have the capacity? And there are the alders, whose leaves invariably just turn brown. And a fundamental question: How does a plant decide when to shut down photosynthesis—there are easily observable differences among individuals of the same species, some retaining green leaves much longer than others. Stress from drought or insect attack might encourage a particular plant to shut down for the season, but what, specifically, are the mechanisms of this response?

Then there are the ferns, for which I have found little information about fall colors. But there is considerable observable variation. On one walk, there were wood ferns with whitish fronds, bracken with dark or light coppery fronds, and lady ferns all black, while in another area, lady ferns were tawny.

There’s no end to natural history questions; one answer just leads to another question! What fun! If we knew it all, there would be nothing left to provide surprises and discoveries.

Autumn bits and pieces

alpine colors, tasty berries, and treats for bird-watchers

I’m inclined to think of fall as ‘dud’ season here. The birds are no longer nesting and few are singing; the forest is silent. Although we have our gorgeous, golden cottonwoods and sometimes some bright yellow willows, we don’t have the dramatic and spectacular show of fall foliage that the Midwest and New England enjoy. The days are getting shorter and shorter. And then there usually is the rain…

However, September brings us a number of good things too. Highbush ‘cranberry’ bushes had a bumper crop again this year, and soon the pungent aroma of cranberry ketchup-making will fill my kitchen. Their pink and red leaves brighten the forest understory. Devil’s club leaves make a fine yellow background for the bright red fruits. Brilliant scarlet dwarf dogwood berries dot the ground. In the muskegs, the leaves of shooting stars are bright yellow spears of light on a darker backing.

But the best color is in the alpine zone. The sedges and avens make a golden-brown backdrop for swathes of deer cabbage, whose leaves run the gamut of color from yellow through orange and red to purple. Dwarf dogwood is here, too, its leaves ranging from summer green to autumn crimson. Low-growing blueberry bushes make a purple-leaved carpet topped with a heavy crop of blue berries. Close up or from a distance, this is a color treat.

The blueberry crops on the ridges are rich pickings this year. With ‘berry rakes’, it is possible for two people to gather over twenty-five pounds in an hour, and leave the patch still loaded with berries for later foragers.

There are two species of low-bush blueberries that grow up on the ridges (and in bogs). One has leaves with smooth edges; the other has somewhat darker leaves with very tiny teeth along the edge. The blossom-end of the berry is slightly different: the one on the toothy-leaved species looks like a small bulls-eye. Once you train your eyes, the two species are readily distinguishable. And, at least for some of us, it is worth making the distinction—berries of the toothy-leaved species (Vaccinium caespitosum) taste better (although the difference may dwindle if the berries are cooked).

In late September, the upper meadows still feature a few late flowers: an occasional purple monkshood, sturdy little clumps of the blue gentian, and lavender daisy-like flowers of fleabane. On the way up to Granite Basin, we even found a thriving stand of miners’ lettuce in full flower, well past its usual blooming season.

Despite the paucity of bird song, there are a few treats for bird-watchers. Hawks migrate south along the ridges—Gold Ridge is a great place to see a variety of species, sometimes in considerable numbers. On a recent trip up to Naked Man Lake on Douglas, we spotted a lone female northern harrier coursing over the meadows and a sharp-shinned hawk dashing into a grove of trees. Flocks of pipits and lapland longspurs flit overhead in open habitats. In Granite Basin, we watched a flock of twenty-five or thirty ptarmigan fly up-valley and disappear behind the ridges. And occasionally, a soft, winter song of a dipper can be heard along the streams, or a song sparrow may trill from a shoreline thicket.

Townsend’s solitaire. Photo by Bob Armstrong

On the upper slopes of Ben Stewart, we saw a pair of Townsend’s solitaires, presumably on their way south. This long-tailed thrush is a rather rare bird around here; it is more common in the open forests of the Interior. It typically nests on the ground on open slopes, cutbanks, and even cliffs, often tucking the nest under an overhanging rock, log, or tuft of vegetation. Summer foods include all kinds of insects and other invertebrates. But in winter, in montane woodlands down south, it commonly feeds on juniper berries. This food resource is so important that each bird defends a territory around clumps of juniper trees, to help ensure its winter food supply. Other fruits may be eaten, especially if juniper berries are scarce.


Even though it signals the onset of dark days, snow shovels, and slippery streets, I rather enjoy watching the termination dust gradually increase on the peaks. At first it’s just a beautiful powdered-sugar dusting on the highest crags. It may disappear for a spell, but the inevitable accumulation is imminent.

The last throes of summer

in the ecotone between seasons

Early September—and Gold Ridge earned its name in a botanical (rather than a mineral) way; the open slopes were covered with the golden leaves of deer cabbage. Color accents came from the scarlet berries and crimson leaves of dwarf dogwood. There were even a few scattered flowers of about ten species still in bloom, with little hope of pollination, but swathes of partridgefoot, still flowering, clothed a few protected pockets.

Black crowberries and two kinds of low-bush blueberries offered snacks to foraging birds and hikers. The very last salmon berries hid under drooping foliage.

A female grouse and a big chick tried to be invisible at the edge of an alder thicket; their patience outlasted ours, and we eventually went on up the trail. A very small marmot hustled into its burrow with a big mouthful of dry grass for a winter bed, while an adult marmot posed regally on a rock right next to the trail. The marmots will disappear for the winter very soon now.

Swarms of minute insects danced in the open spaces between the canes of salmonberry. I have no idea what they were, but surely they were in reproductive mode, trying to beat the onset of low temperatures.

On another day in early September, a stroll through the lower muskegs at Eaglecrest found some good patches of still-unripe bog cranberries and some low-bush blueberries. We saw that a few of the dwarf dogwood berries had been sampled by some small animal, leaving a hole but without removing the seed—very different from the more usual rodent foraging, which focuses on the seed, leaving a hollow fruit behind. I have to wonder who might eat the dogwood berries; I’ve seldom found the seeds in the hundreds of bird or bear scats that I’ve inspected.

A few swamp gentians were still tightly furled in bud and were probably too late for pollination, as were the one or two bog kalmias that were still open. We searched for sundews and found only three decrepit specimens where earlier there had been thousands, so we concluded that they had gone to bed for the season.

Dragonflies—the big, blue darners, mostly—still cruised the ponds and waterways in search of occasional prey. One enterprising couple flew by in copula: the male clasped the female behind her head with the grasping appendages at the end of his body, and the female looped up her abdomen under the male’s thorax where his sperm are stored. He carried her around while his sperm were being transferred to her ovaries (and perhaps he also displaced or removed sperm from a previous mating!). She would probably lay her eggs in dead wood or vegetation, where they would overwinter.

Meanwhile, the sockeye run in Steep Creek ended, and we await the arrival of the coho. The mallard ducks that visit my home pond are all in brown, eclipse plumage. A few, however, are starting to show rusty chests and darker heads that will turn green as the males don their courtship feathers. Mallards begin their courtship and mate-choice in winter—it seems to be a gradual process.

Cottonwood and devil’s club leaves are turning golden, willows sprinkle their crowns with yellow leaves, and the maples glow with yellows, orange, and several shades of red. Highbush cranberry leaves turn to pink and red, and the wild crabapple leaves get a characteristic shade of rather grubby, rusty red. Even some of the blueberries, especially in the alpine zone, are colorful. The alders get left out of this color show; their leaves turn dull brown and crinkled. Why are they so different?

Amid hundreds of ripening rose hips, I saw a single, lonely pink blossom.

“Tis the last rose of summer

Left blooming alone.

All her lovely companions

Are faded and gone”

Autumn on Gastineau Peak

a walk in the clouds

Early September, and fall has been here for a couple of weeks already. Cottonwood leaves are turning gold, and alder leaves are drifting down into dull, brown heaps. Fireweed has gone to seed, except for a few stragglers that bloomed late. The air feels like fall is here.

Warblers are on the move. Mixed-species flocks of little birds flit through the alders and willows. Townsend’s warblers in fall plumage hobnob with chickadees, orange-crowned warblers, and two species of kinglets, along the banks of Montana Creek. Near Steep Creek, orange-crowns forage with chickadees, kinglets, and myrtle warblers. The birds move rapidly among the branches, feeding on tiny insects. The warblers and ruby-crowned kinglets are headed south for the winter, but golden-crowned kinglets and chickadees stay, toughing it out. Two cedar waxwings pass quickly through, not part of a flock.

One cloudy day, Parks and Rec hikers headed for Gastineau Peak. As usual, some started at the Basin Road trailhead and came up through the mud, while others just took the tram, joining forces at the upper tram terminal. As we went up toward Gold Ridge, the clouds settled in around us, restricting visibility to a narrow strip along the trail.

Wildlife viewing was therefore very limited. We saw one marmot just below the trail, looking up at our ghostly forms with apparent puzzlement. I saw the tails of three robins disappear into the mists, and an unidentified sparrow dove into a conifer thicket. And that was it, for wildlife.

Deer cabbage, avens, and blueberry leaves were coming into their fall hues. Most of the flowers were finished, although there were a few valerian, monkshood, and moss campion to be seen, and some broad-petaled gentians, which almost glowed in the mist. Partridgefoot and the hardy little harebells were still doing well.

Our goal was Gastineau Peak, and we wound up the rocky trail in the clouds. No vistas rewarded us, of course, and the wind was rising rapidly. So, after reaching the peak, we back-tracked to the junction with Gold Ridge and huddled in the lee of a bank by a dried-up pond to gobble a quick lunch. A small, gray and white, very tired butterfly wobbled across the stones at our feet and took temporary refuge on a wet pant-leg.

Back on the trail, we were slammed with a sudden, driving, sleety rain, and gusting winds stiff enough to make balance sometimes dicey. Nothing for it, just put your head down (and your hood up), put one foot in front of the other, and make rueful jokes as the rain found its way inside your raingear. We wondered if the tram would still be operating.

This lasted all too long. When we got down near the windsock, the curtains parted, and we had a good view of Bear Valley, in all shades of green, with the little creek calmly flowing through it. Downtown appeared. No more worries about whether or not the tram was running. From there on, it was ‘cake’.

As we left the lower tram terminal in our sodden, wind-blown state, a tourist remarked that he wished he were where we had been! He persisted, even after I told him what it had been like. Poor guy, he must have been very bored. Hmmm, maybe it was OK, after all! We were, in fact, glad we went, but hot showers and hot tea were sounding really good!