Late-summer bricolage

a colorful songbird, a dragonfly encounter, and other observations

Good news from Kingfisher Pond: the male Common Yellowthroat that has been singing and hanging out in the low vegetation apparently got a mate! Because this species is uncommon here (although not in some other regions, hence its English name), I had wondered if a female would show up, and there was evidence that one did so. In mid-July, he was seen carrying loads of captured bugs, presumably to juveniles lurking somewhere nearby.

Photo by Helen Unruh

Revisiting Kingfisher Pond in early August, I found well-grown broods of ducks and a male red-winged blackbird who was still singing and frequently giving his warning whistles. So I guessed that he had some fledglings somewhere in the sedges.

On the West Glacier Trail I saw some agitated fluttering down on the packed dirt. I stooped to look more closely and saw a cluster of small, brown moths(?) having a serious tussle. Aha—one of them was a female, just a bit bigger and paler than the others. Two males were fighting to have-at her, wrestling and twisting and flapping so vigorously that that whole group skittered across the ground. Two other males were flitting about, hoping to join the fracas. The action went on for several minutes, and finally one guy won. She then wandered off with him, backward and upside down, still attached to her by the tip of his abdomen.

As I was bent over, hands on knees, watching that little show, other trail walkers passed by, giving me a wide berth. One kind soul inquired if I was OK and, being told that I was watching something, quickly departed. Not one passer-by asked what I found to be so interesting. Hmmm.

Above the tram on lower Gold Ridge on a foggy day, we found the frog orchids blooming. When we started back down the trail, a huge porcupine shuffled aside to let us pass and then moved a foot or two more into denser vegetation. Clearly it was not much worried by our presence and just wanted to have its lunch undisturbed.

On the Horse Tram Trail, toadlets from the big Amalga diaspora were still crossing the lower part of the trail in early August. I even found an extremely small one (less than 1 cm long) at the top of the hill, far from where most of the dispersers were observed.  It was accompanied by a grown-up toad about two inches long, an unusual association and presumably temporary.

Along that trail, some of the bunchberries had been chewed—something had left deep divots in the fruit, exposing what remained of the white interior. Slugs are the suspected perpetrators. But one day I found a little green caterpillar chewing on the red outer skin of the fruit, so there could be more than one nibbler involved.

Photo by Mary Willson

That observation made me think about larger consumers of bunchberries: What about vertebrates? The fruits are edible (if not especially tasty), and many kinds of vertebrates in other places are known to eat the berries. The list of vertebrate consumers is long, including grouse, thrushes, vireos, and sparrows, as well as black bears, marten, rabbits and hares, and rodents. Most of these critters would digest the fruit pulp and disperse the two small seeds inside each fruit. But what happens here? Some of the consumers on that list live here, but somehow, so far, I haven’t seen evidence of much vertebrate activity on bunchberry.

In early August, near Crystal Lake in the Valley, I was checking out the status of high-bush cranberry crops, which were just starting to ripen. Along came a German couple, exploring some Juneau trails on the multi-year adventure of sailing all over the world. They asked what I was doing, which led to a long chat on various topics. As we talked, a big dragonfly known as a blue darner came in, appearing to be very interested in us. It stayed with us for a long time, perched on our caps, our shoulders, our hands, and seemed quite happy to have its photo taken at close range. We all had fun with him, but I still wonder what he thought he was doing!

Photo by Mary Willson

Meanwhile, back at the ranch, I’ve been enjoying the numerous chickadees that throng the seed feeder over the pond—when the big blue bullies aren’t hogging it. A few juncos are here too, including some portly juveniles from midsummer broods.

Autumn arrives…

…gradually!

Fall is unofficially here, whatever the calendar says: fireweed has gone to seed, sending parachuted offspring into the breezes. Geese are numerous on the wetlands, with more arriving from time to time; more flocks are landing in the big meadow near the Boy Scout camp. Some male mallards are showing signs of developing their breeding plumage. Robins are flocking up and shorebirds have gone south. Cottonwood trees have a few golden leaves, which are released one by one to float gracefully to earth.

Most of the wildflowers (at sea level) have finished blooming. The tall stalks of cow parsnip stand sere and brown. Here and there I can find the very last flowers of lupine and beach pea, but yellow rattle and yarrow still have some fresh flowers, and yellow paintbrush looks good. Among the late bloomers are hemlock parsley and purple asters (not to be confused with the purple daisy, which usually blooms earlier at sea level). Marsh felwort is always late to appear.

The woods are showy with red berries: bunchberry, elderberry, baneberry, the native species of mountain ash, and devil’s club. It has been a good year for high-bush cranberry too; some of the flexible branches droop with the weight of fruit.

Here are a few observations from the last half of August:

–We spotted two small Columbia spotted frogs near lower Dredge Creek; they are known to breed in this area and at the community gardens.

–As I drove Out The Road one day, I noticed severe alder defoliation over long stretches of roadside. The woolly alder sawflies, assisted by the green alder sawflies, have been busy skeletonizing the leaves.

–I recently learned a new plant—a non-native perennial that appears in spots around here. I noticed it in a big clump at the beginning of the Horse Tram trail near the Eagle Valley Center. I was pretty sure it wasn’t a native, so I took a specimen to the Arboretum for the expert horticulturalist to identify. It’s comfrey (Symphytum officinale), known to gardeners as an exotic,noxious weed that spreads itself by thick underground stems(and presumably by seeds, but I found no information about seed dispersal). The pink flowers are pollinated by nectar-gathering bees, which are said to shake loose the pollen by vibrating their bodies when they are inside the flowers, but some bees can be nectar robbers and not pollinators. It is reported to be poisonous, but it also has medicinal uses.

–Along the dike trail, on the lower section before the gazebo, we noticed large stands of another invasive, exotic plant: hemp nettle, native to Eurasia. There are several species in the genus (Galeopsis). The small pink flowers are said to be bee-pollinated, but the species in our area may self-pollinate. This annual plant earns its nettlesome name by the fact that it is spiky all over (almost). The stem bears small sharp spines, the leaves are a bit bristly, and the narrow calyx that cups the base of the flower has major spines, several millimeters long. Woe betideany critter that bites or grabs this plant.

Hemp nettle

The seeds have no special device for dispersal and probably just fall to the ground, but they don’t remain viable for more than three years. A flower can make severaI seeds, which lie in the base of the cup formed by the calyx. Each plump seed is almostthree millimeters long. I was fascinated to learn that, in Europe, the seeds of an unnamed species of Galeopsis are harvested and cached by Willow Tits and used for winter food. I wonder how they do that (assuming that the birds harvest the seeds directly from the plant and not from the ground). For the species we have here (G. tetrahit), the narrow calyx cup is six or seven millimeters deep, rimmed with five sharp spines about four millimeters long. If the hemp nettle species harvested by willow tits is similar, wouldn’t the birds get stabbed in the face? And I also wonder if our chickadees will learn to do this!

–Another local naturalist observed some juvenile ravens at Eagle Beach. One of them carried a spruce cone, laid it down, and deftly extracted the seeds, one after another. Where did it get the idea—maybe from watching some other critter? Had it done this before? In any case, this seems like unusual and interesting behavior.

Photo by Bob Armstrong

Thanks to Elizabeth Graham, FSL-USFS, for info on alder sawflies, Ginger Hudson at the Arboretum for identifying comfrey and showing me the hefty rhizomes, and Bob Armstrong for the raven observation.

Bricolage

this and that from various explorations

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.

Whelks

…and a growth form of hemlock

In the course of looking up some other information, I came across an interesting tidbit about whelks. Whelks are predatory snails; there are many species, belonging to several genera, some of which occur in our intertidal zones. Whelks generally feed by extending a proboscis that has a mouth, leading to the esophagus and stomach, and a file-like radula, bearing lots of small teeth, that shreds the flesh of the prey—conveniently near the mouth. The rasping teeth on the radula are replaced quickly when they wear out. Whelks often feed on bivalve molluscs such as clams and mussels, barnacles, and also various other invertebrates. Access to the body of the prey is commonly achieved by drilling a hole in the hard shell with the radula, assisted by secretions of a chemical that weakens the shell. In other cases, whelks insert the proboscis through a partially opened bivalve shell, sometimes wedging open the two parts of the shell with the edge of their own shell.

Dogwinkle (Nucella). Photo by Aaron Baldwin

Here’s the bit that sparked my interest: Whelks can learn! In lab experiments, European dog-whelks (genus Nucella, related to ones that occur here) were fed on mussels for three months and then were presented with barnacles as prey. Initially, they drilled through the outer shell of the barnacle, but after sampling just a few barnacles that way, they began to shift methods: They started to enter the barnacle through the opercular plates (valves that barnacles open and close when they feed on small prey).This mode of entry is easier and quicker than drilling thru the barnacle shell, so the profitability of whelk foraging effort increased.

Similarly, dog-whelks that were initially fed on barnacles and then encountered small mussels learned to focus on the thinnest parts of the mussel shells. When presented with large, thicker-shelled mussels, they learned to attack the shell at a point above he most nutritious part of the mussel (the stomach area). So, although the foraging effort was high, the food reward for that effort was high.

It turns out that they can also learn to avoid areas when members of their species have been injured or eaten by predators. And they can remember that for several weeks.

These whelks can learn by experience, although they don’t have a real brain. Instead, they have a set of paired nerve clusters (ganglia) in a ring around the esophagus. Those ganglia are well-connected to each other (and the rest of the body), but this arrangement is not called a brain. (Hmm, I know some critters with proper brains who do not learn so quickly!)

Western hemlocks sometimes have trunks that are deeply ridged and furrowed; this is called ‘fluting’. The ‘flutes’ are the furrows; the ridges are referred to as buttresses. Fluted hemlocks are most common along the coast, with western exposure, in situations where the trees are exposed to wind (e.g., near beaches and shoreline cliffs, in clearcuts or other openings). The so-called buttresses and adjacent roots develop most strongly on the side away from the strong winds. In Southeast Alaska, fluted trees are common in the dominant trees of even-aged stands.  Here, we see them commonly on west Douglas and near Auke Rec.

Fluted hemlock trunk

Flutes start to develop where branches emerge from the trunk, particularly when the branches in the lower crown of the tree become senescent and die. Researchers have suggested that branches interrupt the flow of nutrients to the cambium (the layer under the bark that lays down wood, among other things) in the trunk, and nutrients are not distributed equally around its girth. So the annual growth rings are not the same thickness all around the trunk—creating the ridges and furrows.

Cross section of fluted hemlock

Flutes often start to develop near the base of a young tree. They gradually get deeper and deeper, sometimes (after many decades of tree growth) closing right over the bark in the furrow. Then the flutes are not so readily visible from the outside.

It seems that most of the research about hemlock fluting was done some years ago. Many questions are still out there. Why are western hemlocks particularly susceptible to fluting? What about mountain hemlocks? Exactly how does a branch change nutrient flow to the cambium? How do fluted trunks compare to cylindrical trunks in resisting wind? Are there certain genetic strains that tend to develop flutes or that favor windy habitats? And so on…

Thanks to Robin Mulvey, USFS, for help in getting references on hemlock fluting.

Wild animals with injuries

Surviving against the odds

If a vertebrate animal has broken bones or lost the use of a leg, its chances of surviving for very long are usually small, and we seldom note their passage. Most die of starvation or predation. Sometimes a hardy or lucky individual manages to go on making a living for a considerable time, and there are a few scattered reports –a rabbit with a healed hind leg, or a shrew with a separated fracture in one leg, and an elk with a healing leg fracture. A couple of long-legged wading birds with misaligned leg fractures managed to survive. A few non-migratory curlews on a tropical island survived several years with broken wings and even a mallard (victim of hunting) is recorded with healed breaks in a wing. A rough-legged hawk was able to snag prey such as a rabbit even though it had only one functional leg; that leg later healed. 

Much of the evidence for such exceptional individuals comes from museum specimens that became specimens long after their wounds had healed. A nice example is a lynx in Spain: an old female had lost one foot, yet she had recently produced a litter of kits. Gray squirrels in Georgia showed healed fractures in thirty-seven specimens of a sample of over ninety specimens, including seventeen with healed long-bone fractures. A study of several species of small mammals in northeastern U.S. found that thirteen to twenty-five percent of adults had healed broken bones. 

These critters had survived despite serious impairments. They lived by the motto of a centenarian who (as various body systems faltered, one by one, and began to fail) said: “you just have to get on with it!” A coyote in Gustavus has been doing just that: this one has only three functional legs; one hind leg dangles uselessly. But for over a year, it had been hunting for itself, even making those wonderful leaps that pounce down on some rodent in the grass. 

Photo by Katherine Hocker

Many animals are able to self-amputate a leg or a tail—the list includes some spiders, crabs, centipedes, true bugs, salamanders, and lizards (notably NOT birds or mammals). This capacity is well-documented as a means of distracting or escaping predators or, in the case of arthropods, to free a molting individual from being stuck in its old exoskeleton. A self-amputated leg is even used by certain male invertebrates as copulatory plug after he’s mated with a female, to prevent other males from inseminating her.

There is, however, another possible function for self-amputation: reducing the damages associated with a serious injury. All the animals listed above are known to break off an injured appendage upon occasion, but the adaptive value of doing this has been little studied. A study of the leaf-footed cactus bug showed that there is, in that species, an advantage to cutting off a seriously injured leg: individuals that self-amputated survived better than those that did not. However, it was not clear exactly by what means survival was improved.

Self-amputation has costs, of course: the animal has to function without that limb at least until it regenerates or do without it. There may be some loss of body fluid and a risk of infections, although self-amputation takes place at particular places where healing may occur quickly. And there is the additional metabolic cost of regenerating the lost limb, if that is possible. To be adaptive, the benefits have to outweigh such costs.

Waiting for spring

Looking forward to the awakening season

As February became March, the longer days and a streak of relatively warm days meant that folks on the trails were greeting me with “It smells like spring!” and “Spring is in the air!” Of course, we weren’t really done with snow—one day in the second week of March, I slithered and slewed, creeping through deep slushy snow on the North Douglas highway, and my driveway was thick with the same.  More snow came a few days later.

Critters and plants are getting ready for spring, too. Ravens carry sticks to build a nest. Eagles are building too, bringing sticks to a growing platform that will, one day, hold some eggs in a soft cup. Mallards are seen in pairs on the wetlands; mergansers too. Juncos begin to sing, but not yet in full voice. There is a report of snow geese, the first of their kind this year.

Eagles nest-building. Photo by Jos Bakker

Plants also know what’s coming. Skunk cabbage pokes sharp green tips of folded leaves above the surface of ice-fringed ponds. Buds on elderberry and cottonwood are getting fat, preparing to send forth young leaves in a few weeks; buds on the rose bushes at the end of the dike trail are also showing promising signs. Woolly cinquefoil on a rocky outcrop above the beach shows green leaves tucked under old brown foliage.

Meanwhile, we’re still ski-ing the campground and the Montana Creek trail. The big lake and the ponds in the Valley are still covered with (softening) ice. The slate-colored form of dark-eyed juncos that visit us from the Interior are still here, coming to feeders along with the local Oregon form.

We all have signs of spring that we await eagerly and greet with glee. Here is a sampling of favorite signs from a few trail-walking friends (a few of these examples have happened already!):

–Pussy-willow catkins, males presenting pollen

–the squalling of varied thrushes

The first crocuses on a sunny bank. Photo by Pam Bergeson

— the first bumblebees, coming to crocus flowers and willow catkins

–mermaids’ purses (egg cases of long-nosed skates) washed upon a particular North Douglas beach

–the rollicking song of ruby-crowned kinglets

— early yellow violets

–wren songs from the thickets

–footprints of a bear, just emerged from hibernation

–arrival of sapsuckers, their drumming and tapping and calling

–the appearance of rufous hummingbirds (in addition to Anna’s, some of which stayed all winter)

–a flight of shorebirds on their way north for the nesting season

Spring swans. Photo by Jos Bakker
Blueberry flowers. Photo by Bob Armstrong

–alder catkins starting to get soft and limp, in preparation for releasing pollen

–the refreshing aroma of cottonwood buds (after some warm days and nights)

Looking for signs of spring as they develop is a big part of the pleasure in taking a walk at this time of year. Given Juneau’s assortment of microclimates, we can expect to see things happening at different times in different places. And the lookingwill only get better in the next few weeks!

Birds’ sense of smell

…they do have one!

A long-standing myth says that birds have no (or very little) sense of smell (olfaction). Myths usually have long lives, and this one became dogma despite many casual observations suggesting that birds can smell. Only gradually, over many decades, and facing lots of resistance, has the myth lost strength—and finally we can say with certainty that the myth is effectively dead. Birds do have a very functional sense of smell and they use it in many ways (just as mammals do).

Scientists have determined the genetic basis of the olfactory sense and birds have the requisite genes for appropriate receptors. Studies of birds’ brain activation during exposure to odors show definite responses, usually very specific to particular odors. The olfactory bulb of brains varies in size, but even the very small ones (representing a lower number of olfactory receptors) have exhibited clear functional responses. Anatomy, electrophysiology, and genetics back up interesting observations and experiments that clearly demonstrate the variety of uses for the avian sense of smell. Some examples follow:

The myth of no-sense-of-smell began to be perforated by the late 1900s; although at first, the few documented examples were just ‘exceptions’ to the dogma. The examples accumulated, and a number of birds were generally acknowledged to use olfactory cues for foraging. For instance, kiwis of New Zealand have a long bill with nostrils at the tip, and they use that long sniffer to grub for earthworms in the soil. Woodcocks in the northern hemisphere do that also. Carrion-eating turkey vultures can detect the aroma of freshly decaying meat (not rotten) far downwind of a carcass (sometimes misled by the same odor coming from leaking natural gas pipelines). Seabirds such as albatrosses and petrels can follow the odor plume of an aggregation of krill for miles, until they reach a concentration of that favorite planktonic crustacean. In Europe, storks can trace the smell of newly mown grass to find meadows for hunting bugs and rodents. European great tits and blue tits track down the volatile chemical aromas emitted by pine trees that are assaulted by insects, and there they find lots of prey. 

More myth-perforating information appeared from studies of navigation. For example: Homing pigeons exhibit an ability to locate their home lofts by smell, especially in conjunction with using visual, landmark cues. European starlings can return to their nest sites after being experimentally displaced for long distances, if their sense of smell has not been blocked. Shearwaters can navigate over the open ocean, back to their nesting colonies, using their noses.

Furthermore, several kinds of song birds, including European starling and blue tit, can detect the presence of predators such as weasels; parent birds spent less time visiting their chicks if the nest cavity was decorated with the scent of weasels. Hummingbirds often forage on flowers, but they are deterred by ants—not just the presence of ants but even the aroma of the ants’ formic acid (which they can spray to deter their own attackers). Several kinds of birds (e.g., starlings and blue tits in Europe, russet sparrows in China) add aromatic herbage, such as yarrow, milfoil, and wormwood, to their nests. The effects of the greenery seem to differ among the species, often leading to better chick growth–in some cases reducing parasites (ticks, bacteria), or reducing mosquito bites at night, or somehow improving the parents’ incubation patterns, and even affecting mate choice.  

Such observations and experiments completely shredded the myth and demolished the dogma. But there was still skepticism about the use of smell in social relationships among birds— Canbirds identify kin, sex, and the identity of individuals? Can theyuse olfaction in avoiding conflict or in courtship and mate choice? Oh yes! Many studies now have shown that the avian sense of smell is sufficiently finely tuned to be used in these ways too. Here are some examples:

Some birds can self-identify: kiwis can discriminate between the odor of their own feces and that of other individuals, and are said to show territorial aggression when another individual has been detected nearby. Some petrels and prions can identify their own nest burrows by scent alone, avoiding conflict that would occur if they mistakenly entered someone else’s nest burrow. Blue petrels can identify their own eggs and avoid those of other conspecifics.

House finch males can assess the quality and social rank of other males. Spotless starlings can tell the sex of other individuals by their odor, and male mallards get really revved up by the smell of females in the courtship season. Kin recognition by smell can be accomplished by some species (e.g., storm petrels, house sparrows, zebra finches), in some cases avoiding mating with kin, in other cases preferring to associate with kin. Antarctic prions can recognize their mates by smell. Young zebra finches can recognize the odor of their siblings and the natal nest.

How do the birds make such particular identifications? It’s likely that genes involved with the immune system are involved (as they are in mammals, including humans). These genes vary a lot among individuals and are known to affect odor (somehow).They may be dispersed over the birds’ bodies when oils in the preen gland at the base of the tail are spread over feathers as the birds preen to keep feathers in good condition. These genes have been associated with mate choice in house sparrows and petrels. House sparrows make mate choices in part on the immune system, avoiding individuals with too few immune-system genes, preferring those with a good diversity of those genes.Blue petrels prefer mates with immune systems differing from their own, although that was not the case for Magellanic penguins.

An intriguing example comes from crested auklets, a colonial nester on sea cliffs around the Bering Sea. In the courtship season, they engage in the endearing behavior of ‘ruff-sniffing’—nuzzling each other’s feathers at the nape of the neck. The feathers there are specialized, emitting a citrus-y aroma, which comes from certain volatile lipids called aldehydes. These compounds can deter ectoparasites such as lice, and one of them seems to indicate that the owner has good metabolic stress responses (perhaps indicating status and making it a good potential partner). Auklets are attracted to the scent, and sometimes the ruff-sniffing involves several individuals. Birds emitting lots of this aroma can transfer more parasite deterrent and they are more attractive; they are likely to be favored as mates. If the possible status-indicator is transferred, the recipient might then falsely advertise its (unearned) status. These parts of the story needs more study.

Crested auklets. Photo by Gary S. Drew

We can expect to see more and more research revealing that birds can use their olfactory sense in many different social ways.

For more on auklets’ ruff-sniffing, see this article.

Redpolls and siskins

Flocks of winter seed-eaters

In early February, on a damp and drizzly day, a friend and I went out the Boy Scout trail to the beach. The lichens were fresh-looking and happy in the humidity, but nothing much seemed to be happening in the bird world. Then suddenly a flock of small birds came fluttering in from somewhere and settled in the grasses of the bid meadow. They were redpolls, dozens of them. They fossicked about in the bent-over grasses, searching for seeds and probably anything else that might be edible. I watched one demolish a dark, flat seed-head (probably yarrow) completely, seed by seed. A report from Gustavus noted that redpolls were eating lots of yarrow seeds, sometimes riding the seed stalk to the ground, and lying on their sides on the snow to consume the seeds.

A little later, we perched on a low ridge with the trees as a windbreak and watched another group of redpolls work the grassy berm above the beach, occasionally dropping down to the beach itself. I don’t think of redpolls as ‘beach birds’, but on a different day a friendly birdwatcher reported them foraging in the tidal wrack at Auke Rec. They are versatile foragers, often swarming over alder trees, probing the cones and sending down a scattering of fallen seeds onto the snow.

Common redpoll. Photo by Bob Armstrong

Redpolls eat many kinds of seeds and must snatch up bugs opportunistically. They breed in the far north, but irrupt in large numbers every two years or so, when the seed crops fail up north. Then they appear in more southern regions. Redpolls are well equipped to deal with cold weather: their plumage is heavier in winter, they can store seeds overnight in an esophageal sac, and at times they tunnel under the snow and roost for the night under the white blanket.

They sometimes come to bird feeders too, but they may have to share the bounty. Pine siskins, which sometimes follow a two-year cycle but often irrupt irregularly, eat many kinds of seeds, as well as bugs. A Gustavian friend recently reported huge siskin flocks at a feeder, not much disturbed by the human nearby.When they weren’t busy gobbling up sunflower seeds, they bullied any other birds that came to the feeder, driving them off. Siskins are known to be feisty and aggressive, even challenging larger birds.  

Pine siskins. Photo by Bob Armstrong

Out of curiosity, this friend reached a finger out toward one siskin that was perched on the feeder, driving others away and methodically dragging seeds out. It didn’t leave, even when its tail was touched; it kept grabbing seeds. The friend then stroked its back and touched its feet. But this siskin could not be interrupted in its seed-gobbling. Then it stepped up on my friend’s finger and still kept grabbing seeds. We call them little piggies…and I have another name for their feistiness that rhymes with their acronym PISI.

Fallen sunflower seeds accumulate below seed-feeders, and the bird feed on them there too. Enter another actor: a red squirrel. My Gustavian friend watched a squirrel dash out to a crowd of siskins busily eating seeds on the snow, scattering the birds in all directions. The siskins came back quickly, only to have the squirrel spook them off again. And again, and again. The squirrel didn’t seem interested in the seeds; it was apparently more interested in mischief!

Siskins and redpolls don’t really look very much alike, seen close-up, although they are similar in size. Siskins show flashes of yellow feathers in wing and tail and have heavy brown streaks on the chest. Redpolls have fewer brown streaks in front, a black chin bib, and the reddish crown that gives them their name; males usually show a wash of reddish on the chest. Despite these differences, and being classified in different genera, redpolls and siskins occasionally hybridize!

Wood

A marvel of biological engineering

After some big winds, there were lots of downed trees over the trails. Trail crews soon cleared the ways, leaving the cut ends of tree trunks where we could count the growth rings, if we chose to do so. Seeing those exposed rings, plus thinking about the twisted trunks of some pines, made me contemplate wood a bit—wood as a biological entity, not as a commodity to be sold or a nuisance to be removed.

Growth rings are the cross-sections of xylem tissue (as botanists call it, from the Greek work for wood), constituting what we call wood. In temperate zones, rings are produced annually by living trees. Underneath the bark is a special tissue called cambium, which lays down xylem cells toward the center of the tree and other tissues, called phloem, on the bark side. Phloem carries carbohydrates synthesized by the leaves down to other parts of the tree; special horizontally oriented ray cells bring those carbos from the phloem to the xylem. The xylem tissues provide water and mineral transport from the roots to the leaves, support, and water storage. There is thought to be a limit (set by gravity and other factors) to how high a tree can lift a column of water (between 400 and 426 feet), and some redwoods come close.

In general, wide growth rings indicate good years for growth and narrow ones indicate poor years. The first wood laid down in spring has larger, thinner-walled cells, so it is less dense and light in color, while darker, denser wood is added later in the season. This color contrast is what makes it relatively easy to count the rings. Sometimes the rings are not symmetrical—wider on one side of the tree than the other. A tree that leans(e.g., if exposed to regular strong wind pressure or a fallen one presses against it) can develop more wood on the side away from the pressure, helping to make the tree grow upright. 

Photo by Mary Willson

Each layer of xylem contains a variety of cell types, including starch storage cells and others. But here I want to focus on the cells that comprise the hydraulic, water-conducting system. The passage of water in this pipeline is controlled partly by the amount of water taken in by the roots, partly by conditions along the pipeline, and mainly by evaporation from leaves at the upper end (called transpiration by botanists). Water molecules are polar (with a positive and a negative side), so they tend to cling together, and the entire column of water is pulled up when these molecules move from the leaves to the air. The pipeline is very narrow, and capillary action with the sides of the pipe makes water movement relatively easy. Leaves have openings called stomata that can open to keep water moving or close to conserve water. This system can run into trouble if the tree is subjected to freeze-thaw cycles when frozen fluid pushes out air bubbles that tend to break the water column and stop the flow (an embolism, as sometimes form in animals’ blood vessels). The problem can be exacerbated if the water supply is low, as during a drought.

As a tree grows and ages, the older xylem stops conducting water and becomes darker; it retains its support and storage functions (we call it ‘heartwood’). The younger wood (‘sapwood’) has the water-conducting function but is also important structural support.

Although wood density may be mostly genetically controlled, growing conditions (shadiness, soil fertility and moisture, etc.) can also influence characteristics of the hydraulic system, including the amount of leaf surface and stomata that releasewater and the water-conducting cells themselves. Most tree populations exhibit considerable genetic and environmentally plastic variation.

The water-conducting pipelines of conifers and flowering plants (called angiosperms—woody species include maples, alders, oaks, etc.) are different. Conifer pipelines are composed of ‘tracheids’, spindle-shaped cells, tapered at both ends, with lots of pits along the sides. Adjacent tracheids are offset from each other but their pits are matched up, so water can zigzag from one to another. In a tall tree, water may pass through many thousands of tracheids and matched pits on its way up to the leaves. These pits have an intricate, specialized valve thatcontrols flow from one cell to the next, contributing to a tracheid’s ability to recover from an embolism and reducing the risk of an embolism passing from one tracheid to another.Conifer water-transport systems are relatively narrow andresistant to freeze-thaw cycles. Most of the structural support in conifer xylem comes from the tracheids. These cells die as they age but can maintain their conducting function for years.

Illustration by Katherine Hocker

The woody angiosperms have some tracheids too, but structural fibers do most of the support and (in most species) their principal water-conducting pipeline is made of cells called ‘vessels’. More columnar and wider than tracheids, these cellshave sizable openings at each end, guarded by valve-like control devices. They line up one above another, and water can move straight up the pipe. This arrangement is thought to give these plants greater capacity for water movement, but they seem to be more vulnerable to freeze-thaw cycles than conifers. In one study, comparisons of many angiosperm species found that those with greater transport efficiency had less embolism resistance, and these differences were associated with water availability in the species’ habitats. More comparative studies will surely discover more variations that are related to environmental circumstances.

Details of these hydraulic systems and their functioning are the domain of hydraulic engineers!

Twisted pines and many questions

Why the spiral grain?

Strolling on snowshoes around the Lower Loop at Eaglecrest one gray, damp day, we found, as expected, that conditions forreading animal tracks were bad on the rain-packed snow. So we counted trees instead: we had noticed previously that some of the dead or dying pines in the meadows had very twisted trunks, mostly with an upward twist to the right. So this time, we counted the pines with right or left twists and also checked whatever dead hemlocks or spruces we encountered. This informal, unscientific survey produced a series of questions, largely unanswered.

As a curious naturalist, I find it great fun to generate focused questions, even if I can’t answer them. This essay is an example of how the process goes.

–Is there something particularly about pines that produces the markedly twisted trunks? The other conifers in the Juneau areaoccasionally show such marked twists (but seemingly fewer in proportion to the total population of those species) and we have the impression from other observations elsewhere that deciduous tree trunks don’t generally twist like these pines do.

–If the twists occur predominantly in pines (that casual observation should be verified, of course), perhaps there are intrinsic factors, such as differences in the cells that make the wood, that predispose pines to twist. The principal wood cells of conifers do differ from those of deciduous trees, but do pinesdiffer from other conifers? Or perhaps there are environmental factors, such as exposure to wind and snow, that contribute to twisting? We would need to find a good sample of pines that grew in more protected circumstances to examine that possibility.

–We noted that most of the twisted pines have right-twists. Along one section of the Lower Loop, Righties outnumbered Lefties more than fifty to one. However, a casual check along the CBJ Crow Hill trail found very few twisted pines and there were proportionately more Lefties there.

So now the questions can be asked: Is the predominance of Righties due to some factor of genetics (or very early development)? Is there some environmental difference between the two locations that contributes to the very different frequencies of different twists? Or is it an accident of genetics and who happened to colonize Crow Hill vs the Lower Loop?

–As luck would have it, on the return loop, we spotted a long-dead tree, probably a pine, that had broken off near the base,exposing a central core of straight-grained wood surrounded by many layers of twisted wood. Something apparently had changed as the tree grew—the older growth rings made straight wood but the later growth rings made twist. But what?

It can be frustrating to generate lots of questions for which we have no ready answers, but it is good fun to think about the complexities! Attentiveness to things around us as we walk andthinking about the things we observe adds richness to our strolls.