Eagle Beach at equinox time

Just before the vernal equinox, I strolled in the Eagle Beach area with a couple of friends. The lower reaches of the river bore a few cakes of ice drifting to the sea. We stood on the bank, looking toward the Chilkats, enjoying the view. Then, down around a bend, one of those ice cakes surprised us as it suddenly sprouted a long neck and a head. Oh. Not an ice cake. Presently, the swan spread its big wings and set sail over the estuary. It was too far away to be sure of the species, but it was probably a trumpeter swan, which appear to be more common here than the smaller tundra swan.

Trumpeters migrate through here in spring and fall, and occasionally overwinter in estuaries and ice-free freshwater ponds. We see them in various places, including Amalga and the Dredge Lakes area. They are probably from the population that nests in coastal areas farther north; those that nest in the Interior are more likely to migrate inland. They have a huge wingspan, similar to that of eagles, but they are much heavier; they are said to be the heaviest flying bird in the world.

Trumpeter swans once nested in marshes and ponds across much of North America, but hunting (for meat, feathers, skin), habitat destruction, and lead-poisoning (from ingesting shotgun pellets that sank to the pond bottoms, where swans often feed) decimated their numbers. Thanks to conservation efforts, the species is not endangered now, and many breeding populations are thriving.

They can live to be more than twenty years old, but they mature slowly; they usually mature when four to seven years old, occasionally sooner. They are monogamous, the pair bond usually lasting as long as both birds are alive and well, and the pair often staying together year-round.

On the nesting grounds, they choose freshwater marshes, ponds, and small rivers, building nests on beaver dams and lodges, hummocks, and platforms of floating vegetation. The nests are typically surrounded by water, giving them room for a running take-off when departing. Both male and female work on nest-building, both birds collecting material but the female doing most of the construction. The big eggs are laid at intervals of one and a half to two days (not daily, as in most birds). Both members of the pair incubate the clutch of (usually) four to six eggs, but neither develops an incubation patch on the body…they incubate the eggs with their huge, well-vascularized feet!  

They are territorial, fiercely defending their chosen area at least until the eggs hatch and often, with declining intensity, until the chick fledge. That takes three or four months. Both adults tend the chicks, but become flightless for a few weeks during the summer molt. The young birds stay with their parents throughout their first winter. They forage on submerged and emergent aquatic vegetation, sometimes grubbing up tubers. Birds that winter farther south often forage in agricultural fields, and even digging up potatoes and carrots.

A bit later that day, we wandered out onto the sand flats exposed at low tide. And there was the swan again, walking slowly toward a group of grazing Canada geese. We imagined that it had thoughts of joining the group; swans sometimes migrate and forage in flocks of geese, ducks, and cranes. But these geese would not have it! They went on full alert and eventually took off. The swan then ran across the flats and took off toward the estuary.

Photo by Aaron Baldwin

Along the bank of the lower river, we found a lugworm, lying on the sediments. I don’t know why it was there…They normally they live in J-shaped or U-shaped tubes within the sediment, although they can move out and build a new tube at times. At one end of the tube, they deposit coiled fecal castings on the surface, which we often see when the tides have not washed them away. Fecal deposition may sometimes be a slightly dangerous activity, because a foraging bird or crab may snap up the tail end; however, the worm can regenerate a new one. At the other end of the body is an eversible pharynx with a mouth that engulfs the sediment. The worm then digests some of the tiny organisms and perhaps organic detritus, passing out the partially cleaned-up sediment grains in the castings. Some lugworms can also feed on suspended particles. These worms breathe water, using their external gills alongside the body, when inundated by the tide, but reportedly can breathe air through the skin, when the tube is exposed at low tide.

The sexes are separate, raising the question of how these burrow-dwellers manage to make offspring. The available online reports are contradictory and confusing. The males simply eject sperm out into the water, hoping they can find eggs to fertilize. By some reports, the eggs are held in a female’s burrow and released sperm have to find and enter the burrow; that’s a system that probably works best when the worms live at high densities and spawn at about the same time, as indeed they often do. Then what? The fertilized eggs and larvae may be brooded in a female’s burrow; when still small, they leave and make a burrow of their own. However, we often see gelatinous sacs lying on the surface at low tide; they are tethered somehow to a female’s burrow. The sacs contain eggs or embryos; but why are they lying on the sediments?

Advertisement

Where curiosity can lead

Remember Kipling’ story about the Elephant Child and how his ‘satiable curiosity kept getting him into trouble with other animals? The Child asked so many questions, of so many different animals, and the impatient adult animals just would spank him. But the Child persisted, eventually asking a crocodile what it had for dinner. Invited to come closer, the Child got his nose grabbed by the crocodile. When the Bicoloured Python Rock Snake helped pull the Child to safety and the crocodile finally let go, the Child’s nose was ‘badly out of shape’! When the Child protested about his new, long nose, the Bicoloured Python Rock Snake told him that ‘some people don’t know what is good for them.’ And that’s how the elephant got its trunk!

For better or for worse, some humans share the Elephant Child’s ‘satiable curiosity. Readers of these essays often ask me where the ideas for the essays come from. Well, there are several sources: sometimes something I’ve read, or something someone observed, or something I’ve dredged up out of my past research. And sometimes the idea starts with a simple observation, that leads to more observations, some literature searching, and eventually there is a chain of curiosity-driven questions and, if I’m lucky, answers. Here is a simple, recent example:

Swans were back in the Mendenhall River by late March. They were feeding in the shallows, pulling up great gobbets of vegetation. Curious about what that vegetation might be, the observer took a sample to a local expert on algae, who opined that it was a filamentous green alga and gave it a name. Having a name allowed us to do a little digging on the internet and in the literature. What would have been most useful would be information on nutritional value, who else eats it, season of availability, and so on. Alas, in this case, we couldn’t find much that was useful for present purposes. So that lead petered out.

However, among the algal filaments were tiny insect larvae that looked like midges. So a local expert on aquatic insects was invited to take a look. On the edges of the ice were hundreds of cast-off ‘skins’ of midge larvae. That told us that some of the midge larvae had been transforming into flying adults and emerged from the water into the air to look for mates.

Searching the surface of the snow, we found a number of crumpled, dead midges. There was no way to tell if they had completed their reproductive mission or died before they could mate. Eventually we spotted a living female, with thin antennae, crawling slowly over the snow. Shortly thereafter, we found a male, with fluffy, plumose antennae full of sense organs for finding females.

Having the adults in hand, it became possible to get more specific identifications. So a photo of an adult midge was sent to a national midge expert. Getting specific IDs of insects very often depends on microscopic examination of tiny body parts and the distribution of minute hairs, so from a photo alone we couldn’t expect to get a species’ name. We did, however, learn the name of the group to which these midges belong, and that allowed us to dig up a little information about them. They are non-biting midges, occurring in many aquatic habitats around the world. The aquatic larvae of most of the species in this group eat decaying leaves that fall into streams or pools. They can be important decomposers of vegetation, thus contributing to nutrients available in the stream. A study on a small rainforest stream in British Columbia found that the midges decomposed alder leaves faster than cedar leaves, and that cedar was decomposed faster when alder leaves were also present.

While wading in the shallows for another alga sample, we noted that the mud was covered with duck footprints, probably made by mallards. The mallards may be been feeding on the alga, but it likely that they were also preying on midges that were struggling out of their larval skins.

Thus, starting with swans, the chain of curiosity-driven inquiry led to algae, thence to midges and their role in stream ecology, and to mallard foraging. And that’s how it goes; one thing leads to another. No doubt the chain could be extended still farther! Sometimes our own ‘satiable curiosity may get us into trouble, like the Elephant’s Child, but most of the time we can have a lot of fun (without getting our noses pulled out of shape!). Sometimes maybe we even know what is good for us…

Swans

One of the great treats of fall is finding a group of these huge white birds hanging out on a pond somewhere, maybe resting, preening, feeding a bit, or just gliding elegantly from here to there. The swans I see here are usually are trumpeter swans. They really are big: the wingspan is about six and a half feet, in the same size range as that of an eagle. But they weigh about twenty-two to twenty-six pounds, more than twice the typical weight of an eagle.

Their feet are correspondingly large. We are used to seeing the webbed footprints of ducks and gulls, but one could fit several duck footprints into a single swan footprint. Years ago, I stood with a couple of friends on the snowy ice of the Old River Channel, marveling at the footprints of swans, which are six or seven inches long. Given the size of the bird, perhaps this is not disproportionate.

Photo by Jos Bakker

Trumpeter swans that nest in Alaska generally spend the winter somewhere along the coast of Southeast Alaska, British Columbia, and Washington. They could be found anywhere there is open water and food, but some spots are particularly attractive, such as the Skagit Valley and waters near Vancouver Island.

Swans are primarily herbivorous, eating aquatic vegetation, but they also ingest invertebrates along with leaves and tubers, and occasionally eat fish and fish eggs.

Trumpeters are very territorial when nesting, defending their space not only from other swans but also from various other waterfowl. They are monogamous, sometimes just for one season, sometimes for the long-term. Both male and female build their nest (mostly the female), and she may start to lay her eggs before the nest is quite complete. The usual clutch size is four to six eggs, laid almost two days apart. Incubation, mostly by the female, starts before the clutch is complete, so the eggs do not hatch synchronously. Rather than incubating their eggs with the warm skin of a featherless brood patch on the belly, as most birds do, trumpeters cover the eggs with their huge feet, which have a good supply of blood vessels that carry warm blood.

Incubation takes four to five weeks. When the eggs hatch, the chicks (called cygnets) are brooded for a day or two; after that, the adults may brood them at night and during bad weather. When the cygnets leave the nest, they follow their parents for three to four months, learning how to find food. The adults actually help the very young cygnets, by treading the mud to stir up vegetation and invertebrates. The average brood size in Alaska is reported to be about three cygnets. Sometimes broods of different parents join up, possibly as a way to increase access to food (more stirring) or to decrease the risk of predation (more eyes looking).

They are slow to reach maturity, typically taking four to seven years before they breed. In any one year, however, only a fraction of the population is reported to breed.

Formerly widespread and abundant, trumpeter swans are now much reduced in number, because of habitat loss and overhunting. Breeding populations are scattered across central Alaska to the Midwest, the Pacific Northwest, and western Canada. Some of these remnant populations are still at risk from loss of good habitat and lead poisoning (from lead shot and fishing weights). This species is now protected—it is illegal to hunt trumpeters (as of 2017), and restoration efforts have led to a moderate increase in numbers.

The tundra swan, also called the whistling swan, is considerably smaller, weighing roughly thirteen pounds. It breeds in tundra ponds across the Arctic of North America and Eurasia. On the nesting grounds, tundra swans are territorial and monogamous; the pair bond is commonly maintained year-round. They mature at age three to five years. Both parents tend the three to five eggs, for about a month, and attend the growing cygnets. Our populations migrate south to winter mostly on the east and west coasts; those from western Alaska stay in the west, while those from the north go to the east coast. Family groups often migrate together.

It is legal to hunt tundra swans, but not trumpeters, so it is important to be able to distinguish the two species. One criterion is obviously size: tundras are roughly two-thirds the size of trumpeters, by weight. Their wingspan is about five and a half feet, less than that of a trumpeter. The shape of the forehead of tundras is steeper than on trumpeters, which have a more sloping profile. Viewed face-on, the border of the forehead where it meets the bill is either rounded (tundra) or v-shaped (trumpeter). And tundra swans usually have a yellow patch at the base of the bill near the eye, a patch that trumpeters lack.

The hunting pressure on tundra swans is high, and only some of it is within the regulations. Many more are killed by hunting outside of the regulations, including native subsistence, than by the regulated hunts. Undoubtedly, some trumpeters are killed illegally, sometimes by mistake, sometimes clandestinely.

Beach-walking in late March

What’s a restless naturalist to do, when most of the ground in covered with soggy snow and strong signs of spring seem reluctant to appear? Although the varied thrushes and juncos are singing, and the skunk cabbage has poked up in some places, some of us get a little impatient for more. One option for our edification is walking the beaches in hopes that something of interest will show up (it almost always does!).

On the way to Crow Point via the Boy Scout trail, small gaggles of garrulous geese flew from the river over to the far end of the wide, flat meadow. (Do they ever stop talking, except maybe when sleeping??)

Crows were beach-combing, dozens of them, all scattered along the line of the advancing tide, perhaps nabbing small prey that were activated by the onward rush of water.

Overhead, winging northward, were three elegant trumpeter swans. Although most trumpeters nest in the Interior, a few nest near the north end of Lynn Canal. It’s always a treat to see them, if only in passing, and that was the main ‘payoff’ for post-holing my way out to the beach. There had been strangely little foot traffic out this way, so post-holing was the only way to go.

On another day, for no accountable reason, I suddenly was possessed of the notion to look for mermaid’s purses. These are the egg and embryo cases of skates (relatives of rays and, more distantly, sharks). So I went to a beach where I’ve occasionally found them before, washed up on a big tide. Bingo! I found four of them: one black, dry, and dead, two much fresher, yellowish green, but ripped open, perhaps by an enterprising raven, and the embryos gone. The other one was intact, and I tossed back into the water, in case the embryos had survived their stay on the beach.

A short chunk of timber had washed up on the shore of Eagle Beach. It was completely riddled by smooth tunnels, about the diameter of a finger. Aha! Teredos had been at work. A.k.a. shipworms, for their unpopular habit of mining into wooden ships, teredos are really molluscs, albeit with a worm-like body. They can get to be over two feet in length, long, soft, and quite slender, with two very small, ridged shells at the front end. Those shells grind their way into wood as a teredo rasps its way along. The wood particles are digested, with the help of symbiotic bacteria that live in special cells in the animal’s gill. Teredos also eat plankton, which are inhaled by a siphon at the rear end of the body, and pass over the gill on the way to the mouth.

A teredo gets its start when a free-swimming larva finds a suitable piece of wood and settles down, attaching itself by means of byssal threads, such as one sees on mussels and other sedentary molluscs. The larva softens the wood at the attachment point, and then transforms into the adult shape and starts boring. Naturally, the tunnel gets bigger as the teredo grows and moves ahead.

Teredos are somewhat related to piddocks, another kind of clam that tunnels into hard substrates (and which have appeared in these essays before). Piddocks are clearly recognizable as a type of clam, but the stout shell is more curved and has ‘teeth’ along the edge. Piddocks use their burrows just for shelter and filter-feed on plankton, like ‘normal’ clams. A likely evolutionary link between teredos and ordinary piddocks is a group of distinctive wood-borers that use symbiotic bacteria to aid digestion, as teredos do, but the shells are more complex and substantial than those of teredos, a little more like the huskier ones of piddocks. Tunneling into wood (and rock, in the case of piddocks) is the way of life for a considerable array of clams, apparently, a surprising twist on our conventional view of more familiar, sediment-dwelling clams.

At Twin Lakes, the ice was dotted with open holes. A friend watched a river otter that was actively fishing—it caught and ate almost a dozen fairly small fish in a couple of hours. Then it caught a starry flounder; an eagle was watching and came down to snatch it away, but the otter saw the eagle coming and dove quickly, holding onto its prey. Later, the otter caught a big staghorn sculpin, hauled it out onto the ice, and began eating it, looking around for that thieving eagle. Down came the eagle, very fast, and ripped the sculpin right out from the otter’s feet. The otter dove beneath the ice, and the eagle had a good breakfast.

The moment before the theft. Photo by Jos Bakker

Thanks to Aaron Baldwin, ADF&G, for expanding my knowledge of teredos and their relatives.