Good finds in Gustavus

stealthy spiders, ambitious amphibians, strange ferns, and more

A summertime walk through woods and meadows is almost always good—birds are singing, flowers are blooming, and there’s always nice fresh air. But sometimes all the little pleasures form a base on which rest some observations of particular interest. Here are a few good ones from a recent trip to Gustavus.

–Dandelions had mostly gone to seed, so fields that had been golden with flowers were now white with plumes on mature seeds ready to disperse on the wind. But here and there we found a laggard flower, still yellow and conspicuous on the background of white. On one of these late bloomers there was a bumblebee, a strangely immobile bee. Looking more closely, we saw a yellow crab spider with the bee in its clutches. Crab spiders are venomous (to insects), immobilizing their prey and then sucking out the juices. Dinner was in progress and the bee would fly no more. Crab spiders are generally ambush-predators; some of them lurk on flowers in hopes that a tasty insect will alight. The color of the spider often matches the color of the flower on which it awaits a victim.

crab-spider-howard
photo by Kerry Howard

–The ponds at the gravel pits are a great place to see shorebirds, swallows, and kingfishers. There were sticklebacks swimming around and, in June, there were gravid females full of eggs. One pond held many thousands of toad tadpoles, swarming in the shallows where the water temperature was salubrious. They came in a variety of sizes—some at least six times bigger than the smallest. A female toad can lay thousands of eggs; the hordes of tadpoles that we saw undoubtedly had many mothers, which probably laid their eggs at somewhat different times, accounting for the size variation. None of them had begun to transform into toadlets; no little legs were visible. A dense pack of tadpoles clustered around a silvery object, each one trying to grab a mouthful. Looking closely, we discovered that the silvery object was a dead stickleback. Toad tadpoles commonly feed on algae and detritus, but they are also known to scavenge carrion and even the dead bodies of their comrades. Toad (and frog) populations have declined dramatically almost everywhere, and it was heartening to see this large aggregation of juveniles.

–Gustavus is noted for (among other things) its wide sandy beaches. On our way out to one of them, we heard some odd sounds, rather like the hooting of a small owl. As we listened carefully, however, it became apparent that several snipes were performing their aerial territorial display. It’s called ‘winnowing’, and it’s made by the rapid passage of air over the spread-out tail feathers, usually as the bird dives toward the ground from high in the air. Usually the male does this but sometimes females do too. I hadn’t heard this display for a long time and it was a gladsome sound.

–Out on the sandy beaches we found windrows of long, flexible tubes that were the former housing of certain marine worms. The worms were long gone, possibly starved at the end of winter when food is scarce. Then the tides presumably stripped the empty tubes from their attachment points and piled them up on the beach. This observation stimulated a lot of conjecture but no concrete answers.

–On the vegetated sand dunes there were lots of the strange little ferns called moonworts (a.k.a. grape ferns). They don’t look at all like ferns to the layman’s eyes, because the fronds are generally not very lacy or branched. We found many that appeared to be the common moonwort, but there were also a few much more robust individuals that were certainly a different species. On one of the postglacial-uplift meadows we found another kind, one that is now classified in a different genus; the fronds on this one (so-called rattlesnake fern) are somewhat more ‘fern-y’. All three of these are widespread species in North America and even beyond, but they are so odd that it is always fun to find them.

–The pilings of the public dock usually offer something even to a casual observer. Enormous white anemones, far larger than any we usually see in the rocky intertidal zone, wave their tentacles if the tide is in. Sea stars cling to the vertical surfaces too, but the largest ones have trouble hanging on when the tide goes out and leaves them above the waterline. Colorful sponges and tunicates add to the array. Sometimes there’s a giant whelk laying a coil of egg cases. Small fish sometimes gather under the docks and are visible between the pilings. And while one inspects the fauna on the dock, barn swallows are swooping overhead, gathering flies and mosquitoes for their chicks.

–We searched for lady’s slipper orchids (of which more, later). One clump of flowering stems still included a stalk with last year’s seed capsule, well dried. Someone opened the capsule to see if any seeds were left and found, instead, a tiny spider guarding her minute ball of orange eggs. We were sorry to have destroyed her safe-house!

–Sweetgrass grows in many Gustavian meadows and some of us stopped to braid some stems. Braided sweetgrass is used, especially by Native Americans, to construct baskets and decorative items, and we had to try just a simple braid. As we concentrated on our task, we heard thundering hoofbeats, getting rapidly closer. Turning around, we saw a fast-trotting female moose, followed by a young calf. They were so intent on getting away from whatever startled them that they ignored us and passed by, barely thirty feet away, and off they went, full tilt.

Drama on the home pond

aerial attacks on fuzzy chicks

A great ruckus arose on my pond, one afternoon in early June, while I was leisurely scribbling, comfortable in my big easy chair: agitated high-decibel quacking of mallard. Of course, I leaped out of my chair to see what was happening, just in time to see an eagle swoop up from the pond into a spruce tree, dropping a couple of feathers as it landed.

Quickly, I checked the surface of the pond—a female mallard had been bringing her brood of ten tiny ducklings (not much bigger than my fist) to the pond to forage. There was a special place on the far side of the pond, right next to a tuft of weeds, where she would call them to come and rest under her wings. Having watched this family for a few days, of course they were ‘my’ ducks and I didn’t want them to become an eagle snack.

I immediately counted the little ones—no easy task, because they were scooting all over the pond, in and out of cover. But finally, all were accounted for. Mama mallard went on quacking, about one quack per second, for the next two hours. Upon consideration, I guessed that the eagle’s failed attempt had been on the female herself; a duckling would hardly have made one mouthful.

That eagle sat in the tree for over an hour, all of its attention clearly focused very intently on the duck family. It was not distracted by a bunch of juncos flitting about in the tree or around the seed feeder, or by me going out on the deck. A hummingbird close by its head warranted only a sidelong glance. Twice in that long span of time, the eagle thrust forward its head and started to lift its wings, as if to launch a new attack. But then it settled down again, one foot tucked up under its feathery skirts.

Meanwhile, the little ducklings often ventured out from the shelter of overhanging alders to forage. They were adept at diving and scuttled over the pond surface in all directions. Mama duck managed to call them back periodically, only to have them scoot out again. But she herself seldom went far from those protective alder branches.

After more than an hour, the eagle did some intensive preening and took off, but the female duck went on quacking, loudly and constantly. All the ducklings scattered over the pond, foraging actively, while mama continued to fuss. About thirty-five minutes later, back came the eagle and made another pass. Failed again and went to perch in the spruce tree. This time, however, it was very inattentive, fidgeting and looking all around, and it flew away after about five minutes. Needless to say, during all this activity, I got no writing done at all.

The departure of the eagle was a relief for both me and the female duck, although she went on protesting for another hour. The little ones were, naturally, oblivious of the threat, responding only to the need for food and (sometimes) the instructions of their mother.

Several days later, all the little ducklings were still accounted for. They were bigger now, maybe almost twice as big as before. Mama duck had more trouble fitting them all under her wings when they rested. In addition, on the pond was a solo female, who probably lost her eggs to a predator, but who was assiduously attended by a male that was still nattily dressed in breeding plumage. So perhaps she will have another chance to rear a brood.

This was the first time I’d ever seen an eagle at my pond, in all the twenty-five or more years of watching. There has been the occasional pygmy owl, and several goshawks. All the ‘gos’ were in brown plumage, i.e. not that of an adult male. Some of their attacks were successful. Of course, I have to wonder what predatory events I might have missed, while otherwise occupied.

Another day, another place: the day after the eagle threat, Parks and Rec hikers went to Cowee Meadows. We always go there in June (some of us go twice) to revel in the wildflower show. This is the fantastic meadow where we have, several times, recorded over seventy (!) species of flower in bloom in June. This time, we didn’t count them. Nevertheless, we enjoyed a good showing of lupine and buttercups; shooting stars were still splendid and the wild irises were just starting to open. More will come, later.

Some welcome news is that the state park crews have been working on the muddy, root-y parts of the trail, making it easier and safer for walking. They were at work on this day and we all said a big thank you. Yay, State Parks!

Vocalization and predation

begging chicks, whispering whales, and clicking moths

Four baby juncos, in a nest tucked under a dropping clump of grass, lie low and are very quiet. Only when their parents come with food do they raise their heads and beg. When the parents leave, the chicks again are still. There’s a good reason for this: a nestful of lively, loud chicks would probably attract predators, who are always on the watch for succulent little morsels. Even the repeated back-and-forth trips of attentive parents are often enough to alert watchful predators to the location of a nest.

The nestlings of many other songbirds (robins, sparrows, warblers, etc.) behave in the same way, for the same reasons. They nest in open-cup nests, which are vulnerable to all comers. Cavity-nesters, such as woodpeckers, can be a little more brash in their protective holes. Predators may come, but only some of them can enter or reach into a deep cavity, and if they do, they may face a barrage of sharp beaks. Predations rates on cavity-nesters are much lower than on open-cup nesters. As the chicks get bigger, they sometimes perch right next to their front door, poking their heads out and yelling for food (that’s how I easily found the nest of a black-backed woodpecker, some years ago).

Ducks and shorebirds do it differently. Wherever they nest, the chicks leave the nest soon after hatching, typically following a parent around but feeding themselves. When incubation is done, there are no back-and-forth parental feeding trips to lure a predator to a particular place. The family is now a moving target, not a stationary one.

Among mammals that are subject to predation, we find a similar dichotomy. The young of some species follow their mothers, but in other species the babies cuddle in a nest. Humpback whale calves stay close to their mothers, and recent research shows that they talk to them in ‘whispers’—soft vocalizations that cannot be heard at any distance. This may reduce the risk of killer whale attacks. The young of deer, moose, zebras, elephants and other large herbivores are also able to accompany their mothers soon after birth; I wonder if they whisper too!

Young marmots stay near the den, which offers a quick retreat when danger threatens, and young beavers gain some protection from the pond outside the lodge, a haven, when the alarm sounds. Smaller mammals have a variety of arrangements, mostly depending on being cryptic and hard to find.

But some small rodents add another feature that improves safety: They can produce ultrasound: too high-pitched for human ears (hence, “ultra”), these sounds have a very short wavelength along with the very high frequency. Such sounds attenuate rapidly with distance, so they do not carry very far; they are more directional than low-frequency sounds, but they get scattered by reflecting off twigs and leaves. Young lemmings, mice, and rats emit ultrasounds to call their mothers, if they have become separated too long; the calls prompt the mother to retrieve the wandering pups. Although many predators of small rodents cannot hear ultrasound, some can (e.g., dogs and cats and their relatives), and a short-range call of distress might reduce the risk of predation from such carnivores.

Adult small rodents also use ultrasound as a form of social communication within a group, quiet talk among companions. Certain ground squirrels emit ultrasounds that alert others to the presence of a distant threat, the rapid attenuation ensuring that the sound does not carry as far as the potential threat.

On the other hand, some predators have evolved the ability to use ultrasound in hunting—as an aid to predation (rather than a way to avoid it). The toothed whales use echolocation (sonar), much of it in the ultrasonic range, to navigate in turbid waters and to detect their prey. Our resident killer whales, for instance, use ultrasound to locate and capture their fish; the transient killer whales, however, seldom use it while hunting their prey of marine mammals. Not only are the prey mammals much larger and easier to see than the prey fish, typically, they are also more likely to be able to hear the sonar calls of the hunting killer whales. So the transients usually hunt silently.

Bats are perhaps the best-studied predators that hunt using ultrasound. The short wavelengths permit the sounds to bounce off small prey, such as insects, and bats emit very high intensity (‘loud’) ultrasounds as they close in on a hapless bug. Not all insects are hapless, however! Some toxic tiger moths make ultrasonic clicks to warn off approaching bats, which then often abort their attack. Other, nontoxic, tiger moths use their ultrasound to jam the sonar of an attacking bat, making the attack less likely to be successful.

Echolocating calls sometimes also allow the bats to communicate with each other, as they are looking for roosts or food. Because the calls can be individually recognizable, young bats can communicate with their mothers, and friends can talk to each other (although others may eavesdrop). There remains much to be learned about the social uses of sound in bats.