Bird stories

nest-builders, scat-shifters, and spring singers

One day in late April, two friends and I scrambled up a steep stream-side slope to a perch on a cliff below a waterfall. We hoped to locate a nest of American dippers, which have nested in this spot for many years. Although a dipper sat near the pool below the falls, it eventually just flew up over the falls, and we were no wiser about a possible nest location.

However, as we surveyed the pool and falls, another bird was busy, attending to a clump of moss on a spruce branch above us. A male Pacific wren (formerly known as the winter wren) zipped back and forth, carrying twiglets to that mossy clump, which was obviously intended to become a nest. Male wrens commonly build more than one nest, which are inspected by females during the courtship process. When a female selects one of these male-built nests, she adds a little threshold to the entrance, claiming that nest as her own. If a male builds several good nests, he may attract two or even three females who will raise his chicks.

American dipper. Photo by Arnie Hanger

This nest- building male became disturbed at our presence, fidgeting about while peering at us and then finding an elevated perch from which he sang loudly, as if to make sure we knew we were not welcome (songs are how songbirds advertise ownership of their territories). Birds really do not like to be observed when nest-building—egg- and chick-predators such as Steller’s jays are always on the watch for tasty morsels, and the busy activity of a bird carrying nesting material gives away a prospective nest for the jay or other predator to raid.

We go the male’s message and backed away a little. Although he was still nervous, he resumed carrying small twigs and fibers to the growing nest in the ball of moss. Suddenly, the entire bottom of the nest ball fell out! Apparently, the scrawny twigs of the spruce branch weren’t sufficiently substantial to support the structure or all the in-and-out visits of the builder. The wren vanished into the forest.

A couple of weeks later, I returned to this site. Now the tattered remains of the wren’s nest were tipped catty-wompus, barely clinging to the frail spruce twigs. The wren had clearly abandoned this effort and decided to build elsewhere. I could hear him singing, a little deeper into the woods.

On this visit, however, I did see the dippers in action. They were not building in their traditional site in the cliff beside the falls, but under a mid-stream log, instead. These dippers were a bit late in getting started; dippers on some other streams were already incubating clutches of eggs, the incubating females sometimes fed by the male.

In the middle of May, Gold Ridge still had lots of snow, attracting brave or foolhardy skiers up the trail. Ravens were soaring and cavorting, as usual, over the end of the ridge, sometimes peeling away from the group to roll and tumble acrobatically or to chase a passing eagle.

Two ravens perched on a rock outcrop. Both birds picked up something lumpy and white and moved behind another outcrop just uphill. They came back to the first outcrop without the white lumps and picked up two more. They flew downhill a little way, and there they deposited these objects, carefully placing them in nooks and crevices of the rock. Then they flew away.

This time I could see where the white lumps were placed, so of course I went to look. The lumps were the old scats of a wolf and perhaps a bear, all dry and winter-whitened. What in the world did these ravens want with these old scats? Were they playing some kind of game?

Robins and fox sparrows were singing all over the shrubby slopes above the tram. Above the cross, snow still covered much of the ground, and ptarmigan had left the digested remains of their dinners in the places where they had burrowed under the snow in winter. A flock of pipits flew in and began to forage for insects and perhaps a few seeds in the snow-free patches. Pipits look more slender than sparrows and they typically walk and run instead of hop. They sometimes nest high in the alpine tundra on the ridges.

On my home pond, the mallard battles are over. As many as four males hang out amicably, eating seeds that drop from the hanging feeder and sleeping next to each other. No need to fight now; all the females are incubating clutches of fertilized eggs. This is a big contrast to early-season relationships, when each male fiercely defended his female from the attentions of other males. That doesn’t always work, by the way—the interlopers are sometimes successful. Meanwhile, up on Gold Creek, a pair of harlequin ducks was consorting and foraging. She will nest up there somewhere, and when the clutch of eggs is complete, she will incubate them and he will go back out to sea to lollygag with his chums on some rocky point. That’s the way of it, with ducks!


Colors in confrontation

sending messages with feather hues

I once worked in an office in which a co-worker announced that the color red was aggressive, so red clothing should be disallowed in the workplace—or anywhere else!

Well! I’d always found red to be a rather cheerful hue, the color of ripe cherries and raspberries, of wild columbines and scarlet monkeyflowers, of holly berries and Santa Claus. There are some un-cheerful associations with that color, too, such as blood, but to ban a color entirely seemed excessive, to put it mildly. Perhaps you can guess what color my shirt was, the next day!

In the bird world, color is used as part of the process of attracting mates, as we have seen. Color (not just red) is also used to signal social status and levels of aggressiveness.

For example, black-capped chickadees, close relatives of our chestnut-backed chickadees, vary in the darkness of their black cap, and dark-capped individuals enjoy higher social status. Their greater dominance allows them better access to food in winter. House sparrows (those European introductions that can be seen in cities and farms all over the Lower Forty-eight) with high levels of testosterone develop large black patches on the chest. Big patches show other birds that these individuals would win a confrontation. And Harris’ sparrow males that have a high rank in the dominance hierarchy also have large black chest patches. The big black badges signal ‘don’t mess with me!’ There is an advantage both to the males with large patches and the subordinate males with small patches, because they can recognize each other’s status and avoid a direct fight.

White-throated sparrows breed across much of northern North America and occasionally wander into Southeast. Adults, both male and female, come in two color phases. One has black and white stripes on the crown of the head, and the other has brown and tan stripes there (as do juveniles). Detailed research has shown that the black-and-white-striped adults are more aggressive, spending much of their time chasing potential rivals. Although they often obtain and keep the best territories, they tend to neglect their parental duties. So if both members of a pair have black and white crowns, their nesting success tends to be low.

In contrast, a pair of brown-and-tan-crowned adults are less aggressive and markedly more attentive parents. They often lose battles with the black-and-whites and may be forced into suboptimal habitat, where even their better parenting cannot compensate entirely, so their nesting success also tends to be low. Thus, the most successful pairs of white-throated sparrows have one member of each kind: an aggressive black-and-white one and a parental brown-and-tan one.

Experiments with eastern bluebirds (whose appearance is much like the western one) have shown that males with brighter blue plumage out-compete the duller males in contests over nest boxes. So the brighter males get the best nest boxes, and get them earlier, which also gives them first choice of females. I’m tempted to speculate that, like bright mountain bluebirds, they also do well in obtaining extra-pair copulations.

Photo by Bob Armstrong

Red-winged blackbird males have red epaulets with a yellow border. In aggressive encounters with each other, they show off these bright red patches by flaring the wings and erecting the feathers. (You can sometimes see them in the marsh by the Pioneer’s Home or in the big marsh on Eagle River.) They can cover the epaulets with black feathers on the upper back when they want to sneak into a neighbor’s territory unaccosted by the owner. In this case, the optional display of color signals not social status but level of aggressiveness.

In an earlier essay, I noted that much of the variety of color and pattern that we see in the animal kingdom is the result of mate choices and competition to be attractive to the other gender. Another portion of the array of colors and patterns can now be seen to be a result of signaling social status and level of aggression.

I have not addressed the matter of color with respect to camouflage, or signaling age or gender or species, or mimicry, or warning colors, and so on. But all of these things contribute to the diversity we see. Perhaps in a future essay…?

On the Rock

…some early fall observations

Mid-April, taxes are filed, the government didn’t close down, and the sun is shining. A good day to head up the West Glacier Trail in search of purple mountain saxifrage, whose pink flowers are among the first to appear in spring (pussy-willows are the very first). Much of the snow was gone, so we walked along the lakeshore for a mile or so and then cut uphill to the trail.

At the bench, the group decided in favor of dropping down to lake level again, rounding the bay with the big beaver lodge, and going up on the first ridge beside the beaver pond. And there, just above the pond, we found the first blooming purple mountain saxifrage. Soon we were seeing dozens of them on the barren rocky outcrops, with more to come into bloom in the next few weeks.

A bumblebee zoomed by but didn’t visit the saxifrage flowers. Perhaps she wanted to visit the multi-flowered catkins of the earliest-blooming willows.

At the beaver pond, there is a route up the cliff to the top of the ridge, but our group chose our old way. Past that pond, we scrambled up the alder-covered ramp to the next level. The rock terrace here is pocked with small ponds. A pair of mallards had secluded themselves in one of the ponds, well sheltered by shrubbery, but our coming spooked them and off they flew. Here we found more saxifrage, as well as lovely ‘gardens’ of moss and lichens.

At the end of the rock terrace is a crack in the cliffs that gives easy access to the top of the ridge, not far from the end. Here we sprawled in the sun for a leisurely refueling, in preparation for what we knew would be a bushwhack back along the ridge.

And indeed it was bushwhacking at its best, thrashing through the alders that filled the dips between rocky outcrops. So errant twigs snatched my glasses from my face, or knocked off my cap, or snagged on my pack, to the accompaniment of muttered imprecations. However, we rejoiced in the absence of leaves, which were still tightly furled in their buds, so we could more or less see where we were going. Here we found a robin, a plump squirrel, porcupine scat, and some old bear scat full of chewed up ground cone.

On the outcrops were numerous deposits of small scat pellets, not quite as round as hare scat and not in good hare habitat, se we deduced they’d been left by mountain goats. On one outcrop, we found a pile of tiny pellets right next to a pile of bigger ones, suggesting that a nanny with a kid had rested there. Our deductions were reinforced a little later, when we looked back toward the end of the rock peninsula and saw five ambulatory white spots. Three of them scampered agilely up and over the crest of the ridge and disappeared.

Looking down toward the toe of the glacier, we could see the edge of the rather new colony of gulls. Gulls still nest on the southern face of the rock peninsula, but as the vegetation gets taller and denser there, the gulls get fewer. A few years ago, they began a new nesting colony on bare rock closer to the ice.

We regained the West Glacier Trail via the ‘social trail’ that slants up the hillside through the alders. Here, however, the alders are my friends, providing convenient hand-holds.

This trail crosses a steep rock that even the mountain goats go around, judging from white hairs caught in the brush below the rock. Now, however, some thoughtful folks have installed a climbing rope that greatly facilitates passage over this spot.

February notes

porcupine gnawings, worms on ice, and a strange and flabby fish

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

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

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

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

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

Ragfish and friend. Photo by Bob Armstrong

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

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

Camping in the Beardslee Islands

Part 1 of 2

I edged my kayak along the rocky beach and pried myself out (‘T’aint quite as easy as it was a couple of years ago!). An out-going tide meant a long haul up the beach with gear, but soon all the kayaks were safely stowed above the line of beach rye. Presently, a small colony of tents appeared in the meadow, all carefully placed to avoid crushing too many flowers.

The meadow wore a colorful blanket of Indian paintbrush, ranging in hue from deep crimson through all the reds and oranges to a clear yellow. Tiny purple gentians, white-flowered angelicas, and a few lupines added to the décor. Best of all, underneath the taller plants lurked wild strawberries! Some were still in flower, some had little green fruits, and some were just about ripe.

There weren’t as many ripe ones as we might have wished, because some robins and a group of juvenile ravens had discovered the little red (and almost red) treats lying on the moss. The ravens were so intent on harvesting goodies that they ignored us most of the time. The allure of the strawberry fields was very strong for us too, and each of our exploratory walks on this island had to begin with a hands-and-knees crawl to garner whatever the ravens and robins had missed.

The meadow occupied a point on the south end of an island, ideally located to catch breezes from almost any direction, and also give us the opportunity to shift from one side to the other to find the most comfortable amount of breeze. Both sides of the point offered good views of passing humpback whales and sea otters. We were pleased and surprised to see several very large, hefty terns (probably Caspians) fly by.

Our beach gave us ringside seats for watching the young ravens, which provided much entertainment. They fossicked up and down the windrows of torn-up algae and debris on the high tide lines, turning over bits of sea lettuce and nabbing whatever unfortunate invertebrates were exposed. Sometimes they paraded back and forth, holding some prize, as if to tempt a sibling to pursue. And they played ‘stick’ with each other: one juvenile would grab a small stick, approach another and lie down on its side, offering the stick to the other one, as if to say Play with me!

We amused ourselves by looking closely at the paintbrush flowers, which are visited by hummingbirds. The flower is a green tubular structure within the colorful bracts, and a hummingbird has to probe quite deeply to reach the nectar. When it does so, it presses on a stiff lip, which forces the tube to open and expose the sexual parts. Then pollen sticks to the hummers head (probably) until the bird visits the next flower.

Indian paintbrush plants are hemiparasites on various other plants, meaning that, although they have green leaves and can photosynthesize carbohydrates, they also obtain certain chemicals from their host plants. Our red-bracted species is known to parasitize lupines, from which it obtains alkaloid toxins. The alkaloids are stored in the paintbrush leaves and the colorful bracts around the flower itself, where they deter insect herbivores. However, the nectar in the paintbrush flowers does not contain the borrowed toxins, so the pollinating hummingbird would not be affected.

By some miracle, in this summer that so far was characterized by near-record-breaking cool and wet, we were allowed to revel in rainless sixty to seventy degree temperatures for several days. Being all-too-human, we even managed, on one day, to complain that it was too hot! Nice flat water gave us perfect conditions for poking about in bays and inlets, with occasional stops for snacks and terrestrial explorations.

Early butterflies

four species of early Southeast fliers

Starting in mid-April this year, we began to see a few species of early-flying butterflies. In general, Juneau is not blessed with a great diversity of butterflies, for whatever historical and geographic reasons. I also suspect that butterflies in Southeast Alaska have not been as well studied as those in the Interior or, certainly, in the Lower Forty-eight. In any case, it was a treat to see these four kinds of early fliers in April.

Milbert’s tortoiseshell. Photo by Bob Armstrong

–Milbert’s tortoiseshell. Arguably the most colorful of the early fliers, this butterfly has broad orange bands on the upper surface of the spread wings and some red spots at the leading edge of the forewing. On some individuals, however, the orange and red marks are not bright. The undersides of the wings are brownish and much less conspicuous. Males and females are similar. This species overwinters as adults, tucked into crevices of tree bark and buildings. After emergence from hibernation, females lay eggs, which produce a new generation of adults in summer. The larvae feed on stinging nettles, good stands of which are found here in several locations.

Adults like to bask in the sun as they perch on branches or grass or the ground. They visit flowers for nectar and can serve as pollinators by carrying pollen from one flower to another. We saw this species visiting the ornamental coltsfoot the Arboretum in mid-April.

–Mourning cloak. This is another beautiful butterfly that overwinters as an adult. The upper surface of the wing is dark, rich brown, bordered by a wide yellow band on the wing margins. Males and females are similar. A favorite larval food in Alaska is willow leaves, but other hosts are included in the diet elsewhere (and perhaps also in Alaska).

Adults often bask in the sun as they perch. They can be seen visiting the sap wells that sapsuckers carve on willows and other trees, and they also feed on animal dung and decaying organic material. They may occasionally go nectaring and serve as pollinators.

–Blues. There are several species of small bluish butterflies in Alaska, and I don’t know which one(s) we have here. Although the ‘Butterflies of Alaska’ by Philip and Ferris indicates that blues usually emerge and fly in late May or June, at the earliest, in late April this year, hikers were treated to a small, bright blue butterfly flitting along the trail. When it perched with folded wings, the brownish undersides of the wings made it nearly invisible; upon take-off, the brilliant blue was again exposed. This was a male; the females lack the bright blue and are more camouflaged in mottled brownish-gray.

Some blues hibernate as pupae, on the way to transforming from larva to adult, but some pass the winter in the egg stage. Host plants for larvae are varied, and for some species, unknown for Alaska. Eggs are commonly laid in flowers, and the larvae eat the flowers or, in some cases, seed pods of the host.

Blues belong to a taxonomic family (Lycaenidae) in which a number of species are well-known to be part of an interesting symbiosis that may occur in Alaskan species too. The larvae are tended by ants, which guard them from would-be predators. The ants benefit by feeding on excretions from the larval digestive tracts. Juneau, however, does not seem to be home to many ants—I see them only in a few places—and therefore it is uncertain if this symbiosis occurs here.

–Whites. Bigger than blues, but smaller than mourning cloaks and tortoiseshells, they come in a range of whitish-ivory-pale yellow hues. Females are duskier than males. Our whites are currently classified as margined whites; taxonomists call it a ‘species complex’, meaning that they are not sure how many, or which, species are here. I saw several in late April, earlier than the dates given in ‘Butterflies of Alaska’.

The larval host plants are plants of the mustard family. They are presumed to overwinter as pupae. Adults visit many flowers and can be effective pollinators.

All of these species exhibit a particular behavior called ‘puddling’. Butterflies of many species visit moist soil, decaying material, and places where an animal has urinated, sometimes gathering in large, spectacular aggregations. In most cases, these are males. For some species the big attraction is salt, specifically sodium; for others, it is nitrogen. At least in some species, males can transfer the nutrients to females at the time of mating, and this leads to better reproductive success, but we have no information on this from Alaskan species.

As summer comes, there will be more butterflies to see, some of them residents, some of them vagrants. Climate-warming is likely to permit more species to visit or live here–more fun for butterfly watchers.

Communication among plants

sessile green birds

As a young professional, I was interested in animals—how they make a living, how they raise offspring, how they behave. Plants were just things that birds perched on, used as nest material, and produced bird-food such as edible fruits and seeds. Of course, they also used the sun’s light to photosynthesize carbohydrates, generating oxygen in the process. But beyond that? They just sat there.

Quite belatedly, I came to realize that plants could be viewed as sessile green birds, even though (being sessile) they can’t fly or walk, and even though they can do some things birds can’t do (photosynthesis). Nevertheless, they really can do many of the things that birds and other animals do: As plant ecologists have long known, they defend themselves (with spines or chemical compounds), they compete for light and soil nutrients, they sometimes even produce chemical compounds that suppress other plants that try to grow competitively close. More interesting was the revelation that they compete for mates, by developing more attractive flowers to draw in more pollinators, for example, and in some cases they can even choose their mates, by rejecting pollen from certain pollen donors. That provided a direct parallel to what many animals do, and it was an eye-opener for me.

Later, reports began to surface about plants communicating with each other. No, they don’t cry or yelp or speak as many animals do, but they use other means to ‘talk’.

Back in the 1980s, two research papers elicited a strong backlash of disbelief, scorn, and derision. One paper focused on poplar and maple trees, the other on Sitka willow, a western tree that grows here in Juneau. Both papers reported that if leaves of one individual tree were damaged by chewing insects, that individual tree ramped up not only its own chemical defenses but also, surprisingly, the neighboring trees did likewise! Later papers showed that the neighbors don’t even have to be of the same species: damaged sagebrush could cause close-by wild tobacco plants to bolster their chemical defenses. Airborne chemicals (pheromones) from the damaged plant were perceived by neighbors, which then mounted their own defensive response.

As the years passed, the experiments continued and became more convincing, so the scoffers grew less vociferous. However, as far as I have determined so far, there are still some big questions: is this really some form of signal, which implies an intended receiver? Does the initial damaged plant benefit from emitting volatile warnings of potential danger from leaf munchers? If the neighboring plants are genetic relatives, there might be a benefit to them all. Or are the neighbors merely eavesdropping on a signal that the initial damaged plant emitted, sending a quick message to the rest of its own leaves? The story continues to unfold as research continues.

Much less controversial is the underground network that links most of the land plants in a given area. This network is made up of filaments of fungus; some fungal connections extend for tens and even hundreds of meters. Many kinds of fungi contribute to this network: some link only certain kinds of plants, while other have more general associations with a variety of species. The fungi in question here are called mycorrhizae (fungus-root), because they are closely associated and in some cases even penetrate the roots of land plants.

The classical view of mycorrhizal systems has been that carbohydrates from green, photosynthetic plants are transported to the fungus, and the fungi garner mineral nutrients from the soil, transporting them to the green plant. A nice simple symbiosis, in which both partners benefit.

But it turns out to be far more complex than that. Mycorrhizae constitute a system of conduits through which pass not only carbohydrates and nutrients, but also molecular signals of stress resulting from damage and sometimes other molecules as well. Some studies have shown that stress signals from a damaged plant can induce defenses in the receivers in just a few hours, by turning on the genes that control the production of defensive compounds.

Research has shown that the fungal network can connect many different plants, even of different species. A big green conifer tree may supply carbohydrates or defensive chemicals to numerous other plants, not only near neighbors but those that are some distance away. A mycorrhizal fungal network might draw soil nutrients from a fertile area to plants that are trying to grow in less fertile ground. On the other side of the coin, so to speak, it is also possible for biological warfare to occur via the network: one plant can send damaging chemicals to its connected neighbors, suppressing their growth and thus reducing competition from them. The mechanisms by which all these interactions take place are still a subject of study.

Further studies have shown that at least some plants can identify the genetic relatedness of their neighbors, distinguishing kin from non-kin by means of exudates from the roots, probably carried by the connecting fungi. That makes possible discriminatory behavior of such plants…they provide more carbohydrates to kin than to non-relatives, for example.

So what we see as individual, independent plants above ground is really an association of interdependent plants that are connected underground, interacting in a variety of ways. In short, no land plant really stands alone.

Intertidal discoveries…

…include kleptoparisitism

On the next-to-the-lowest tide in late April, some friends and I explored the intertidal zone not far from town. We soon catalogued all the usual beasts, but several observations really caught my fancy.

Three tiny, bright red hermit crabs (very cute!) guarded their protective periwinkle shells with their big claws. We counted over seventy small king crabs, all less than an inch in carapace width. There were lots of five-armed sea stars, but one had only three arms and one had only two arms, with no signs of regeneration. So we wondered about the feeding success of these crippled stars, with so few arms for pulling open clams; how does their diet differ from that of intact stars, and how long does it take to get enough nutrition to regenerate those missing arms?

Among all the small fishes that lurked under boulders were two large crescent gunnels, at least eight inches long. They were so dark that the crescent marks on the backs were hard to see; these individuals were reddish on the lower parts of head and body and were probably males. The heads of two flatfish lay on a low ledge. The bodies of both fish behind the gills had been gnawed off, leaving a ragged margin. Someone had feasted well—probably otters, which commonly eat these fishes tail-first, and crabs may also have picked off a few bits.

The biggest puzzle was a heap of fuzzy-looking snails piled up on a mound of mostly indistinguishable material. We had no idea what this was, so I asked an expert and did some reading. Here is what I learned: These snails are known as Hairysnails (currently classified as Trichotropis cancellata). The shell bristles with hairs, and experiments have shown that the hairs deter some, but not all, predators. This snail lives in the North Pacific, usually sub-tidally, so the very low tide on this day was fortuitous for us.

Photo by Kerry Howard

Hairy snails are sequential (protandrous) hermaphrodites: as they mature they are male first and then gradually turn into females as they grow. Bigger snails produce larger clutches of eggs, increasing their reproductive output, while size is less important to male reproductive success, so for this species it pays to start reproducing (as a male) when small and producing eggs, lots of them, when large. During the transition time, they can sometimes function as both sexes at the same time—researchers have seen pairs of snails in which both snails are being male and female simultaneously.

The feeding habits of Hairysnails are fascinating. They can feed on small organisms suspended in the water but, more interestingly, they are kleptoparasites—stealing food particles right out of the mouths of tube worms (they are rarely seen parasitizing other potential hosts). The tube worms feed by catching plankton on their waving tentacles and funneling the prey to their mouths, and the snails just cling to the side of the tube and reach out with an extended lower ‘lip’ to snap up incoming prey. The snails that we saw were all clinging to a conglomeration of tube worms, ready to snatch food particles when the tide came up again.

Worms thereby suffer a reduced growth rate, but the sneaky, thieving snails grow much better—up to eighteen time faster than when simply suspension feeding. Small, immature snails, including those that are only a millimeter in size, gain the most in growth from their kleptoparasitism, but larger ones are also able to reproduce better. In most places, there is only one kleptoparasitic snail on a given tube worm, but occasionally there are two or even three, potentially in competition for stolen prey.

Hairysnails mate and lay eggs in winter, and in that season the adults generally leave their hosts and occupy themselves with reproductive activities. Males come back to stealing from tube worms when they are done mating, but females tend their batches of eggs for a while, and thus return to their hosts later than the males do. Small snails, less than about five millimeters in size, do not leave their hosts seasonally, but continue to thieve and grow.

Kleptoparasitism, in reference to stealing food from another animal, is widespread in the animal kingdom. Birds are perhaps the best studied: frigatebirds, jaegers and skuas, and some terns are well-known for harassing other birds that have caught a fish, making the victim drop the fish for the pirate to grab. In Berners Bay, we watched young glaucous-winged gulls, acting like teen-age hoodlums, chase other gulls until the prey was dropped. We sometimes see eagles forcing another eagle or an osprey to drop its fish. Among insects, cuckoo-bees lay their eggs on the pollen balls made by queen bumblebees for their own larvae and thus are stealing food from the bumblebee larvae. Web-building spiders may lose their prey to other spiders or to flies. Hyenas sometimes harry lions at a kill until the lions depart, letting the hyenas take much of the lions’ prey; and sometimes lions steal from hyenas. Those are just a few examples, but researchers say that kleptoparasitism occurs in every major taxonomic group of animals. Humans are not exceptions!

Sometimes the concept of kleptoparasitism is broadened to include the stealing of any useful item from another animal. So male bowerbirds that swipe alluring objects from each other, in order to decorate their own bowers, are kleptoparasites. So, too, are penguins robbing each other of stones used in their nests or tree swallows forcing a chickadee to give up its nest for the swallows’ use. Again, humans are not exceptions!

Thanks to Dr. Aaron Baldwin, ADFG, for sharing some of his extensive knowledge of marine invertebrates and providing literature references.