Hawk moths

master fliers and specialized pollinators

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Bedstraw hawk moth (Hyles gallii) Photo by Bob Armstrong

If you walk through a field of fireweed, you might see spittle bugs and aphids and –if you are lucky—a hawk moth. They hover at flowers on their rather narrow wings, extending their ‘tongues’ to extract nectar. They can fly very fast, which may have given them the common name of ‘hawk.’ They’re also called sphinx moths: when a caterpillar is at rest, it raises the front part of its body and tucks the head down; someone with a vivid imagination saw a resemblance to the famous Egyptian Sphinx.

There are well over fourteen hundred species of hawk moth in the world. Some of them specialize on extracting nectar from orchids and often incidentally (to the moth) pollinating them. Many hawk moths have long proboscides (‘tongues’), suitable for extracting nectar from the long nectar spurs of certain flowers. When there is a good fit between the length of the spur and the length of the proboscis, the moth can pick up pollen on its eyes or face and transfer it to another orchid flower. If the proboscis is too short, the moth can’t reach the nectar in a long spur and is not likely to visit that kind of orchid very often. If the proboscis is too long, the moth’ head or body will not contact the place in the flower where the pollen is produced, so although the moth can steal some nectar, pollination is unlikely (unless it happens that the pollen is contacted by the proboscis itself).

Certainly the most famous of these relationships (as I mentioned in an earlier essay) concerns the Madagascar star orchid, whose prodigiously long (eleven inches or so) nectar spur caused Darwin to predict the existence of a suitable moth with an equally long proboscis. Sure enough, someone else eventually found that predicted moth, in action. Now there are rumors that a second species of long-tongued hawk moth can also reach the nectar and do some pollination of this orchid.

A little closer to home, in the swamps of Florida and Cuba, the ghost orchid lives high up on tree branches. The nectar spur is said to be about five inches long (but variable) and it is now known that several species of hawk moth can pollinate this species. Unfortunately, the orchid is now quite endangered, in part because of over-collecting by too-avid horticulturalists.

Slightly closer to Alaska, in the tall-grass prairies, the fringed prairie orchids are pollinated by hawk moths. The western fringed prairie orchid has a nectar spur over two inches long, which is said to be longer than most other North American orchids. It is known to be pollinated by four species of native hawk moths (perhaps more) and by one non-native species (that was introduced to North America from Eurasia to help control an invasive weed). This species of orchid is designated as ‘threatened’, largely because of habitat loss as the prairies were plowed under for agriculture. But in addition, the moths are at risk from pesticides drifting over from the agricultural fields. Some published accounts say that no seed set is accomplished in the absence of moth pollination, but others say that a little self-pollination without the help of the moths is possible. In either case, reproduction is generally poor.

In Alaska, little seems to be known about the relationships of hawk moths to flower pollination. Of the seven species on record in the state museum, only some are represented by more than a few specimens (thanks to the helpful entomologist, Derek Sikes, for this info!). I’ll summarize a bit about three of them. Here in Juneau, we sometimes see the bedstraw hawk moth (Hyles gallii) as the adults visit fireweed and other flowers. Two local orchid-watchers have seen and photographed this moth visiting the white bog orchid, carrying pollen on its fairly long proboscis (about an inch long). Is this moth a regular pollinator of this orchid? Hawk moths elsewhere are known to pollinate related species of orchid, but it has been thought that this orchid is pollinated mostly by moths that sit on the flower while they sip nectar (instead of hovering, as a hawk moth does). In any case, hawk moths seem to be uncommon around here, so their role in pollination may be occasional at best.

Another hawk moth that we occasionally see here is called the hummingbird hawk moth (Hemaris thysbe). The wings are clear, without any colorful scales. This species is known to visit many kinds of flowers, including some orchids similar to the white bog orchid, but how many of these visits accomplish pollination is not known. The proboscis is of medium length (less than an inch), so deep nectar sources are not available to this moth.

One other fairly well-represented species in the museum collection is the one-eyed sphinx moth (Smerinthus cerisyi), which sports pretty blue eyespots on the hind wings. Although I don’t know if it has been recorded in Juneau, there are records from coastal British Columbia and from near the head of Lynn Canal, so it seems possible that we might see it here. It has an extremely short proboscis (only a few millimeters long), and one source states that it is not functional at all. In that case, the adults would not feed and there would no pollination.

Hawkmoth caterpillars are often called horn worms, for the horn-like projection that sticks up from the rear end. The three Alaska species that I’ve mentioned all have ‘horns’, although not all hawk moth caterpillars do. The caterpillars are herbivorous, commonly eating a variety of leaves. Bedstraw caterpillars eat fireweed, plantain, enchanters nightshade, and many other things, in addition to bedstraw. Hummingbird caterpillars eat snowberry, blueberry, cherry, thistle, clover, and more. One-eyed sphinx caterpillars forage chiefly on willow and poplar, but occasionally other species too.

Visiting new territory

dabbles in California natural history

I recently made a visit to California, stopping briefly in Tahoe and the region around San Jose. There was little opportunity to pursue my usual natural history interests, but here is a small collection of observations.

–A chubby California ground squirrel climbed up a manzanita shrub to eat the fruits that give the shrub its name (manzanita means ‘little apple’).

–A family of Brewer’s blackbirds scoured the ground for picnic scraps, the well-grown juveniles still trying to coax tidbits from the parents. These blackbirds were the common avian scroungers in many picnic areas, waiting for visitors to drop tasty bits. Other moochers around the picnic tables included one or two kinds of chipmunks and the golden-mantled ground squirrel, which looks like a big chippie but lacks the head stripes.

–A group of wild turkeys was a big surprise, seen as we whizzed along a highway. It turns out that turkeys were introduced to this area decades ago from the native Rio Grande population.

–A male western tanager posed next to the road, so everyone in our slow-moving cavalcade got a good look at it. Even the non-birdwatchers enjoyed this colorful fellow.

–Both ponderosa pines and Jeffry pines grow at mid elevations here. They look quite similar, but their the spines on their hefty cones are different: those on ponderosa cones stick out and stab the hand that grabs them, but those of Jeffrey cones are bent back and do not stab. If you can’t find a cone for conducting this test, try smelling the bark. Jeffrey pine bark is aromatic, fruity or vanilla-scented, depending on the observer. My nephew and two of his small offspring joined me in smelling the tree trunks; the rest of the clan took this as confirmation of lunacy.

–On a stroll through a coastal redwood grove, I noted that many of the big trees were circled by dense crowds of small juveniles sprouting at the base of the trunk. Redwoods sometimes form hefty burls at the root crown. This type of burl is known specifically as a lignotuber, composed of numerous dormant buds and food reserves. The buds are reportedly stimulated to sprout if the adult is damaged or begins to die. If the adult actually dies, a few of the sprouts can take over that location, surrounding the old stump. However, unlike the very thick-barked adult, the sprouts would be very vulnerable to ground-fire. Burl sprouts also self-thin rapidly, especially at low light levels; at extremely low light levels, all of them die. Presumably, the crowds of juveniles around these trees had not self-thinned much: some of the small trees were several feet tall, despite the crowding.

–In the same grove, a few of the small redwoods had white, not green, foliage. Lacking chlorophyll, these cannot conduct photosynthesis to produce the carbohydrates needed for growth. So they are dependent on their connections to adjacent trees that do have the usual green foliage. Those connections might be direct (root to root) or via fungal links. The white trees are little parasites!

–The Monterey Bay Aquarium occupied me for several hours, gawking happily at the varied displays. A large, tropical comb jelly was fancifully adorned with more colorful frippery and furbelows than any I’d ever seen before (being accustomed to more modest ones, with their rows of cilia around an oval body). The perilous state of the endemic population of vaquitas in the Gulf of California was featured in one area. These small porpoises get caught in fishing nets and drown; they also have already lost most of their food fishes to greedy humans, who ship just a certain body part to China (for pseudomedical sales). Sadly, there are only thirty or fewer still left.

A video of cuttlefish showed the tentacles shooting out with incredible speed to snag a hapless little shrimp. That fascinating sight captivated me, but I don’t know much about cuttlefish, except that they are related to octopuses, nautiluses, and squid, a group of molluscs collectively known as cephalopods. So I looked up a few bits of information. The two long tentacles are hidden among the eight short arms, when the animal is just cruising around. Most cuttlefish are fairly small, with a body length less than about twenty inches long. They travel by jet propulsion (forcing water out through a siphon) and by undulating the fins on the side of the body; the ones I watched also seemed to walk on some of the arms (but that might have been an illusion). Cuttlefish can change color and pattern rapidly and spew forth a cloud of ink to obscure their movements. They have relatively large brains and excellent vision. They don’t live very long, reportedly just a couple of years. Males fight over females and the winner inserts his sperm into the front of the female’s mantle cavity using his tentacles. Males can even remove the sperm of the female’s previous mate, flushing it away (a tactic not limited to these critters, by the way).

And here are some un-natural history observations: It was a short visit, but it didn’t take long to grow weary of congested highways and traffic delays, the many other roads squirming off in all directions (GPS was essential), beaches that were packed with bodies in various stages of sunburn, parks thronged with humans. Almost every flat expanse that wasn’t covered with buildings featured vast agricultural fields of sunflowers or artichokes or other monocultures. Gigantic strawberry fields harbored odd, round-backed creatures near every row—stoop-labor at work. Some enormous fields were entirely sheathed in plastic, reportedly for weed control. Not my idea of a place to live! I was very glad to leave it and come Home!

Hiding in plain sight

camouflage is more than just visual

When the presence of an animal is difficult to detect or it is hard to locate, it is said to be cryptic. Think of a female mallard sitting on her nest; her mottled brown feathers are good camouflage—they make her look like a little heap of old leaves, not readily distinguishable from the background. We may actually be seeing her but be unable to register her presence; we just don’t detect her, much less locate her nest. She is not out of sight, like bunny in a burrow; she is hidden plain sight.

A famous case of background matching was very well documented. The peppered moth (Biston betularia) in the UK likes to rest on lichen-covered tree trunks and branches. The typical form of this moth has white wings speckled with black spots. The wings also reflect UV light, but even that has a speckled pattern. The speckled pattern makes the resting moth almost invisible as it sits on the tree bark.

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Photo by Bob Armstrong

During the Industrial Revolution in England, beginning in the mid 1800s or so, pollution from factories killed off many of the lichens and the tree bark became blackened with soot. Then the typical form of the moth was very conspicuous against the dark bark and they were readily picked off by hungry birds. A mutant form with black wings, much less noticeable on the sooty trees, then became more common. Natural selection in action!

More recently, industry has become environmentally somewhat cleaner, the trees are not so dark, and the black form is vulnerable to predation. As a result, the white, typical form of the moth is again becoming common.

Because we humans are so heavily oriented to visual things, we usually think of visual cryptic-ness (or crypsis). But why not think of crypsis that relates to other sensory systems? There are several studies suggesting that there may acoustic or olfactory crypsis, and hints for other sensory modalities.

–Acoustic signals are used by many animals for courtship or other communication among individuals of the same species. For instance, males of a neotropical frog make complex calls to attract females, especially when several males are calling simultaneously. But in the presence of predatory bats, they simplify their calls, even though the females prefer the complex ones. At the price of reduced attractiveness, the simpler call appeared to make the male callers less detectable to the bats. They didn’t completely stop calling—which would be acoustically hiding. They just became less detectable.

Many small birds produce a high-frequency, thin alarm call (“seet”), which does not carry very far. This is thought to be more difficult to locate than the usual contact or distress calls. Experiments with captive hawks indicated that these predators had trouble locating the source of the sound and attacked less often, when the potential prey used the high-frequency calls. The small birds can hear the call and be on the watch for trouble, but they don’t need to know the exact location of the caller.

–The leaf-eating caterpillars of another moth (that’s closely related to the peppered moth) look a lot like little twigs, which might protect them from birds but not from predatory ants that hunt primarily by smell. Yet such ants just walked over the caterpillars as if they weren’t there at all and didn’t attack them. However, if the caterpillars were transferred to a different food plant, the ants attacked them readily. Then, after the caterpillars had fed on the new food plant for a while and molted to the next larval stage, they were again ignored by the ants. In this case, the protection comes from matching the chemical constitution of the food plant.

Some elaborate studies of herbivorous pine bark beetles compared the chemical signals and the responses of predatory beetles in different areas (California and Wisconsin). Pine bark beetles use chemical signals called pheromones to attract others of the same species. Predatory beetles cue in on those signals. As might be expected, California pine bark beetles liked their own pheromones better than the Wisconsin ones, and vice versa. But the California predators homed in better on the Wisconsin pheromones, and the Wisconsin predators homed in on the California pheromones better than on the local ones of each population. In other words, the prey were less apparent to local enemies than distant ones, suggesting they were chemically somewhat cryptic.

Birds have a preen glad just above the tail that produces oils and waxes that the birds use to dress their feathers. A fascinating study revealed that the normal waxes are replaced by less volatile waxes during the nesting season of several ground-nesting shorebirds. Furthermore, if only the female of these species does the incubating, then only the females show the shift in wax composition. Ground-nesting birds are particularly vulnerable to predation by mammals, and experiments with a search dog trained to the smell of these waxes showed that the dog was less able to detect the waxes produced in the nesting season.

–In addition, there are hints—but only hints—that shifts in electrical fields, or in production of wakes by swimming animals, or in substrate vibrations have the potential to be used by prey animals to whom crypsis could be advantageous. There are, potentially, many ways to be hidden in plain ‘sight’. And many investigations are needed. In the meantime, it is useful and interesting to contemplate things beyond our usual ken.

A big thank you to the gracious CBJ librarians who promptly obtained a necessary reference for me!

Ducks, sundews, yellowlegs, and…

dragonflies, gentians, leaf beetles, and a yellowlegs encounter too

On a hot, sunny day, I sat with some friends on a big log, looking across Berners Bay toward Lion’s Head. The tide was out, exposing some big rocks off to one side. A female merganser with four half-grown ducklings cruised around, eventually disappearing behind one of those rocks. Suddenly two of the young ones came hurriedly splashing around to the near side of the rock. Hmmm, something was clearly awry! They then went behind the rock again but soon reappeared, with at least one of their siblings, on one end of the rock. There they all settled down into what a friend once called “a little pile of cuteness”. What caused the commotion and the retreat to the top of the rock? We blamed a seal, whose head surfaced next to the rock, looking intently where the duck family had been.

What about the female merganser? As she drifted between her resting brood and the shore, an eagle swooped down on her from behind. A narrow miss for the eagle, as the duck quickly dove down. An exciting day for the duck family.

We were staying in the Cowee Meadow cabin and found entertainment on our doorstep. A red-breasted sapsucker regularly visited the logs of the cabin walls, peering around at us on the deck, almost as if it were hoping for handouts. Later, a sapsucker went down to the ground by the fire-pit and picked up several woodchips, filling its bill and taking off with them. Why would a woodpecker scavenge chips when it could make its own, and what did it want with them, anyhow?

The front of the cabin was patrolled by a large dragonfly that flew back and forth between the creek on one side and the nearby trees on the other. A sudden flash of blue emerged from the trees and made a grab for the dragon, but I think the jay missed its mark; soon thereafter a large dragon was again patrolling the front of the cabin.

A few days later, still in the hot sun, Parks and Rec went to up to Cropley Lake. Great expanses of meadow were spangled with thousands of small white stars: swamp gentians. This annual plant is probably pollinated by flies (rather than bees), but there has been very little study.

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Swamp gentian. Photo by Bob Armstrong

A little lower down in the meadow vegetation, we found many tiny, white, five-petalled flowers of the round-leaf sundew. These small insectivorous plants were so common in some areas that they almost made a carpet, although not all were flowering. Experimental studies, comparing sundew plants with lots of captured insects to those with few captures, revealed that well-fed sundews grow better and make more flowers. The flowers have no nectaries, so they have little reward for pollinators; they are capable of self-pollination. However, insects, mostly flies, do visit the flowers at times. So flies can be pollinators but they are also prey for this plant. That seems self-defeating! However, they are likely to be different kinds of flies, as shown for the closely related long-leaf sundew.

On a walk out toward Nugget Falls one morning, I noticed that the cottonwood leaves had been severely damaged. So of course I looked more closely, and I found lots of small black larvae of leaf beetles. They had munched up the surface layers of both top and underside of the leaves, leaving nothing but a delicate network of leaf veins. Adults of these leaf beetles overwinter in the leaf litter and lay bunches of eggs in spring. The larvae pass through several molts as they munch and grow; the early stages (called instars) are often colonial, feeding in gangs; later instars are more independent. Some trees had been much harder hit by these beetles than others, but is that because some trees are just more susceptible, less well protected, or because of chance events when female beetles were laying their eggs?

A friend and I walked up to a meadow on the Spaulding trail to see if the long-leaf sundews were flowering yet. No, but we had an exciting time nevertheless. There were fair-sized shorebird footprints in the mud of the drying ponds and a shorebird was calling persistently from the top of a dead pine. As we turned to go, we got dive-bombed from behind—a close pass ruffled my hair. Then a second attack, accompanied, as before, by loud cries. (OK, OK, we are leaving anyhow…). Those greater yellowlegs were clearly defending something important, and at last we saw it (there might have been more, somewhere)—a big, tall chick, still fuzzy and flightless, sneaking through the sedges. So we went quietly on our way, leaving them in peace.

A group of five mallards in female plumage come to my home pond that same day. They foraged all around the edge, nibbling here and there. Then they went over to the bank on the far side and I expected them to climb up and settle down for a nap, which is what usually happens. But this time, the naps were delayed and the birds were almost hidden in the brush. The blueberry bushes started twitching and jumping, and I could see that the birds were reaching up to !!pick blueberries!! They cleaned out the berries on those bushes and finally settled in for a nap. I wonder how they learned that blueberries make fine snacks—so different from their usual fare.

Geothermal springs

the unusual ecology of a unique habitat

This essay takes me rather far afield from my normal trails, but there are so many fascinating aspects to these springs, and so many things still to be discovered, that I could not resist trying to write about them.

Geothermal sites are scattered over North America, with concentrations in the mountainous west. Water from rain or snowmelt sinks far underground, where the very high temperatures near the center of the earth heat the water. When that water rises to the surface through weak spots in the rocks, its temperature ranges from tepid to very hot. Depending on the amount of water emerging, the spring may be a geyser (if water is under strong pressure), or a warm pool, a seep or mud puddle, or just some steam. Some springs have notable concentrations of dissolved minerals, such as sulfur and salts.

Alaska has its share of geothermal sites—at least 79 of them. Most lie on a line from the Seward Peninsula eastward or on an arc from the Aleutians over to Southeast. Southeastern Alaska is well-endowed with hot springs, whose temperatures range up to about 180 degrees.

Who lives in hot springs? Of course that depends on the temperature (as well as water chemistry and the availability of oxygen); in general, the higher the temperature, the fewer the kinds of things that can live there. If the water is merely warm, there might be algae, some small crustaceans or molluscs, along with some beetles, true bugs, or flies—even a dragonfly! A certain kind of fly (in the genus Ephydra) likes it pretty hot: up to about a hundred and thirteen degrees F. Some hot-springs critters are such specialized ‘thermophiles” (meaning heat-loving) that they live only at higher temperatures. Unfortunately, there appear to be no studies of hot-spring faunas in Alaska, although Ephydra flies have been found in one of them. An obligately thermophilic water-mite is recorded from northern B.C., and I wonder if it might occur in Alaska too.

Few vertebrates can tolerate the conditions in thermal springs, but in North America, some little fish in desert pools have become quite famous—and perilously endangered. These are two species of pupfish (of the widespread genus Cyprinodon). The desert pupfish is less than three inches long, living in springs that may get as hot as a hundred and ten degrees F., reportedly feeding on snails that also must tolerate such temperatures. The Devil’s Hole pupfish is even smaller, about one and a half inches long; it’s found in only one pool in a Nevada cavern at about ninety three degrees F., and there are very few of them left now.

The only organisms known to thrive in extremely hot springs, with temperatures over a hundred and eighty degrees F, are certain bacteria and some similar-looking micro-organisms known as Archaea. These all have metabolisms that are very different from other organisms—their enzymes obviously have to be very heat-tolerant.

Thermal springs influence the vegetation that grows around them, in part because the annual frost-free period is longer. Species such as cow parsnip can grow taller than usual. A study in central Alaska near a hot spring (temperature about a hundred forty-one degrees F) discovered three species (a grass, a fern, and a violet) living around the spring hundreds of kilometers north of their usual geographic range. (That, of course, leaves open the question of how they got there…). Soil temperatures near a spring are often warmer, maybe allowing better growth of species (such as white spruce) whose roots don’t do well in cold soil.

Geothermal springs across the continents seem to attract more public attention as places for people to bathe than as subjects for scientific study. In contrast, the geothermal vents in the deep ocean have made headlines for their rich diversity in exceptionally extreme conditions.

Deep-sea hydrothermal vents are found principally in places where tectonic plates are separating and the sea floor is spreading as new material arises from deep in the earth. They are sometimes also found where two tectonic plates collide and one plate is pushed beneath the other, creating a deep trench. Underwater volcanos create some hot vents too. Some (not all) of these hydrothermal vents spew forth water at phenomenally high temperatures—up to more than seven hundred degrees F; at the great pressures of the ocean deeps, that water doesn’t boil. As the emerging hot water meets the extremely cold water of the deep sea, minerals are precipitated out, sometimes creating tall chimneys around the vent itself.

Nothing lives at those extremely hot temperatures inside the vents, but around the vents and chimneys there is often a very rich community of organisms. The base of the food chain there is made up of bacteria and archaea that metabolize sulfur instead of oxygen (which is scarce down there). An assortment of small crustaceans, shrimp, snails, mussels, limpets, tube worms, clams, and no doubt other things can be found on the warm sides of the chimneys. Farther up the food chain, crabs of several types are predators on the others. Certain species of fish called eelpouts are known from some vent systems, where they feed on tubeworms, crabs and other crustaceans. A tiny octopus (Vulcanoctopus) in the Pacific feeds from the sides of vent chimneys on swarms of amphipods.

In 2015, a deep-sea exploration near the Galapagos discovered a cluster of egg cases of the Pacific white skate near a geothermal vent in an area where the temperature was distinctly warmer than the ambient thirty-seven degrees F. Scientists thought that perhaps the warmer temperatures would speed up the normally very slow (over four years!) embryonic development time (although faster development might require more oxygen, which is limited in supply there). We don’t, apparently, know the fates of those eggs and embryos. A cautionary note is provided, however, by observations of a certain octopus on a deep-sea lava outcrop off Costa Rica. This octopus likes to lay its eggs in the lava crevices, where the mothers tend the eggs until they hatch. But on the geothermally warm parts of the outcrop, the embryos did not develop and the mothers looked stressed, leading the scientists to wonder if all the good, cool incubation sites on the lava were already occupied, leaving no room for the stressed, failed mothers, who had to use what space was left.

Three-toed woodpeckers

a delightful encounter

On a nice June day I was traipsing along the Outer Point trail when I heard some loud chattering. As I got closer, I saw two women standing in the trail, gazing up at the source of all the noise. There was a hole in a small dead tree, maybe ten feet up, and the chatterer’s head poked out. A woodpecker, of course, but which one? The parents were very diligent and also very quick while making their food deliveries, but after several parental visits we were sure they were American three-toed woodpeckers. Oh good, this was a chance to watch a bird that is not very common around here, although they are widespread across North America, in the northern and montane conifer forests.

None of us had binoculars that day, so I went back the next day, better equipped, so I could more clearly see the chick in the nest doorway. It was big enough to fill the entire opening, and it seemed to stay there, with its head near the door all the time I watched. So I don’t know if it had siblings down in the nest behind it. Normally, there might be three or four chicks in a nest. Although it was possible that some chicks had already fledged, if so, they were already dispersed well away from the nest site; I was confident that the parents did not have other chicks close-by. The one in the nest opening chattered incessantly—and I do mean incessantly!—even when it rested its head on the doorway and closed its eyes. Its tune changed when a parent arrived, or came into view nearby, with a load of food. Then the call notes got louder and slightly farther apart. But the regular clamor resumed as soon as the food delivery was accomplished. An insatiable offspring!

The very next day I went back again, with some special international guests, for the chance of seeing a new (for them) bird species. The huge chick was still in the nest, calling and calling, but now with a new little whirr in its repertoire. We all waited for an hour, and then I waited for another hour, but no parent birds came. Disappointing! It was very different from the previous day, when the parent birds delivered little tidbits every ten minutes or so. (The tidbits were really small, and quickly delivered. Very different from another nest I later observed, at which the large loads brought by both parents gave the chicks several ‘bites’.) Was this abandonment, or part of a weaning process, or….?

American-Three-toed-Woodpecker-(female)-and-juvenile-by-Bob-Armstrong
Photo by Bob Armstrong

The next day, the chick slept in the doorway, occasionally making rather soft calls. Two days later, the doorway was empty. I hope the chick fledged and is now following its parents around, begging and starting to learn how to flake off scales of bark.

Both parents usually participate in all phases of nesting: excavating a cavity, incubating (at least both have brood patches), feeding nestlings and fledglings. Males have a yellow crown patch that females lack, but—oddly—chicks of both sexes have a yellow patch, which is eventually lost by females.

The parents had been unfazed by us standing in the trail, just a few feet away from the nest tree. Nor were they bothered by a dog, a small child and her father sitting right below the nest. They obviously persevered through the noisy process of recent trail repair in that area, which must have overlapped at least with the early part of the nesting cycle, perhaps through the approximately two weeks of incubation and the first part of the three-week nestling period. Amazing resilience!

Three-toed woodpeckers forage chiefly by scaling bark on dead and dying trees, using a sideways strike of the bill, and bark beetles are said to be a major food. But they also drill for wood-boring beetle larvae (though less often and less deeply than the related black-backed woodpeckers). Surprisingly, in spring and early summer, at least in some areas, they also make sap wells in bark and sip the sap, as sapsuckers do regularly (although they may not have the brushy tongue that sapsuckers use to lap up sap; I found no information on that).

By why do they (and the black-backed) have only three toes (pointed forward), when most other woodpeckers have four toes (three forward and one back)? It might have to do with how they pound on the tree trunk. To initiate the strike, they lift the whole body away from the tree, standing more or less on tiptoe with heels raised. It is thought that a fourth toe at the back of the heel might interfere with raising the heel as part of delivering the whole-body strike. In addition, the head drives forward. Ribs near the base of the neck are broader than usual, for extra muscle attachment, aiding the strike and stabilizing the neck. So they can deliver quite a wallop.

Ah, but doesn’t such a hard strike hurt their heads? Maybe not: certain muscles related to bill movement may absorb some of the shock and help spread the shock over a wide area.

This and That

sundews, pines, spider and bees

In early June, I went with a few friends to check out some muskegs at Eaglecrest. In addition to the common round-leaf sundew, we found some long-leaf sundews already making flower buds. Both of these diminutive species supplement their income by capturing hapless small insects on sticky hairs on their leaves and digesting their victim’s juices. There seem to be minor differences in their preferred habitats: longleafs are more likely to grow on soils less densely covered by mosses and other plants. For some reason, perhaps habitat availability in part, longleafs seem to be much less common than the other sundew.

Sundews are not our only insectivorous plants. Butterworts grow in the meadows on Douglas, for example, and in the subalpine meadows on Gold Ridge. Their leaves are sticky traps for insects. Bladderwort is a delicate, fragile aquatic plant sometimes found in muskeg ponds; it captures tiny aquatic creatures in ingenious little bladders with a narrow opening. The opening of each bladder is guarded by trigger hairs; when disturbed by a passing crustacean or insect, the triggers signal the bladder to open. The walls of the bladder are held inward under tension, but when triggered, the walls expand, and the lowered pressure inside the bladder sucks in the victim. Nifty!

While we were exploring the Eaglecrest muskegs, we also noticed that some of the shore pines bore tiny red rosettes near their growing tips, usually on the upper branches. What???? Not some other organism that has taken up residence there. I was sure I’d seen these bright rosettes before, but any knowledge of them seemed to have fallen through the ever-widening cracks in what used to be my memory. However, after a bit of discussion, we settled on the right answer—these are brand new seed cones! Other shore pines bore clusters of pollen-producing male cones, just at the right time to pollinate the new cones.

contorta-flower-kerry-howard
Photo by Kerry Howard

Reproduction in pines is a complex business that includes many seemingly strange delays. The new seed cones were initiated the previous fall but don’t emerge as rosettes until spring. Only the upper scales of the red rosettes bear fertile ovules. When the scales of the rosette open up, a drop of fluid appears near the ovule; this is called a pollination drop. It lasts two to four days, and then it is withdrawn, pulling in any pollen brought in by the wind. The rosette scales then enlarge and close; the receptive period is over. However, the pollen does not germinate immediately, and fertilization of ovules occurs about a year after pollination. Then the embryos develop over the following year, and the seed is filled with food for the seedling. However, pollen from another individual tree is more likely to result in viable, filled seeds than pollen from the same individual. Then the seed cone scales enlarge, and after two full years, the seed cone is mature and ready to shed its seeds.

So, if (and that’s a big ‘if’) a twig makes a cone or two every year, observers might see the red rosette at the tip, then a small cone or two where last year’s shoot tip was, and below that, a mature cone ready to shed seeds in fall. Older cones that have long since shed their seeds may still cling to the twig farther down.

Shore pine cones take two years to mature, but there are other kinds of pines in which cone development takes even longer, as much as six years! But why?? For comparison, seed cones in spruce and hemlock mature in the year they are pollinated. What ecological factors account for the great differences in the ‘strategies’ of cone maturation among all these related conifers?

A few days later, a beautiful brown spider, with gold stripes on its long abdomen, clung to the top of a beach-rye seed head. As I watched, it crept out into the space on the eight-inch journey to another seed head, seeming to walk on air. I could see that two of its legs were prodigiously long, far longer than the other six. Then it fussed about on the second seed head for a short while, moved down an inch or two, and slowly came back to the first seed head. Of course there must have been some silk strands in place, but I could not see them from any angle of view, they were so fine. The diligent spider then seemed to lay down some vertical strands across the existing horizontal ones, working on an invisible web. I would like to know how the first horizontal threads were laid down across that sizable gap. I don’t know her name, so I can’t look up anything about this lovely beastie.

The next week, I perched on a log in the sun, with a clump of beach pea on one side and a stand of lupine on the other. Several small worker bumblebees visited the lupines, erratically checking out a flower here or there on different inflorescences, zooming off a little way and then returning. Occasionally, one would open a flower, pressing down on the lower lip, but never stayed more than about one second. Was that time enough to sip some nectar or was this a sign that no reward was available? If nectar rewards were present, why were the visits so erratic?

 

What a contrast with the behavior of a big, fat queen bee, who was all business. She went straight to the beach peas and systematically visited every open or nearly open flower in the clump. Her behavior suggested to me that she was regularly rewarded for her visits—otherwise, why stay