Notes from Gustavus

piddocks, creepers, and a phenomenal feat of swallowing

The good snow was long gone, leaving only some soggy snowplow berms along the roads, where moose and wolves had left their marks, days ago. Our usual occupation on winter walks is finding animal tracks and stories in the snow, but that was obviously not a possibility on this December visit to Gustavus. However, if you turn two curious naturalists loose on the landscape, some things of interest are bound to be discovered.

Here are some of the small things that captured our attention:

–A long series of humps atop the beams and pilings of the fuel dock turned out to be hunched-up great blue herons, pretending to be gargoyles. There were seventeen of them (!), not the record number for one sitting (the record is over twenty), but nevertheless a lot of gargoyles.

–A small flock of white-winged crossbills, calling to each other and flitting from one shore pine to another, sampling the cones. Each bird worked on a cone from above, reaching down over the base of the cone and concentrating on the cone scales close to the tip of the cone, prying open the scales with the crossed bill and extracting the seed. They didn’t spend much time on any one cone but moved quickly on, to sample another one. Were these cones not good providers of sound seeds?

–Beach rye had produced a good seed crop and many seeds had fallen to the sand from the full seed heads. Up north, snow buntings are reported to glean the fallen crop, but who eats them here? The next big tide is likely to wash them all away.

–Piddocks are clams with distinctively curved shells that bear an elongate, flat projection on the inner surface of the shell. That projection serves for the attachment of muscles that are used to torque the whole clam when it burrows into clay or rock. A burrowing piddock can disarticulate its two shells, anchor itself to the substrate with a sucker disc on its foot, and rotate while the two separated shells scrape their way along. Small teeth on the edge of the shells do the grinding (do they sometimes wear out?), possibly with some assistance from chemical secretions. Piddocks are said to live in their burrows their whole lives, enlarging the burrow as they grow. Gustavian beaches are littered with these shells, but I have not found them in Juneau. Why??

–Brown creepers typically forage by hitching up a tree trunk, probing crevices and lichens for small insects and spiders. We found one doing just that, then flying to the base of the next tree and starting upward on that tree. They typically nest behind loose flaps of bark on dead and dying trees, seldom using any other kind of nest site; the bark flap conceals the nest and protects it from severe weather. Once a pair of creepers finds a nest site, they build a little hammock of small twigs and fibers behind the loose bark, and then build a comfortable nest cup of fine materials on the hammock. My friend had found a nest last summer while the adults were feeding chicks, so our curiosity led us to haul out a ladder and climb up to peer behind the bark flap; but the soft materials making the nest cup had disintegrated, leaving just a pile of small bits. The rather specialized nest site makes me wonder how common those favored nest sites might be, and if the distribution of nesting brown creepers might be governed by the availability of good nest sites.

–On the Gustavus dock, several glaucous-winged gulls had harvested sea stars on a low tide, as they often do. We saw one fly up to the dock with a four or five inch sea star in its bill and wondered just how the gull could eat that stiff, prickly, thing with arms sticking out in all directions. So we watched. The gulls repeatedly dropped, then picked up, the star, then finally picked it up and just held it for a long time, with the star’s arms poking out from both sides of its bill. Now what? Well, after almost ten minutes, that sea star simply disappeared down the gull’s gullet. The star must have eventually relaxed, so that the arms folded a bit, allowing it to pass through the gull’s throat and make a big lump in its crop. Even a relaxed star must scratch uncomfortably on the way down. In any case, how much of a sea star is digestible…what makes them worth eating?

Photo by Bob Armstrong

Thanks to Dr. Aaron Baldwin, ADFG, for helpful consultation about piddocks.

Snowy tracks

stories written on the winter landscape

Snowshoes crunched over deep snow. The sky was cerulean blue and the sun gradually crept around the mountain peaks. These were fine days to be out, seeing what we could see. We were especially interested in the tracks left by the wild critters as they went about their daily lives.

–A shrew left a long line of tiny marks by the side of a beaver pond. Short digressions led to tufts of grass or a buried stick, where spiders and bugs, slowed by the cold temperatures, might be found. Shrews only weigh a few grams and have a very high metabolic rate, so they have to eat almost continually. We often see their trails running over the snow and plunging into miniscule holes that lead under the snow blanket where prey might be found.

–Mouse trails are much less common. But one day we found a line of hopping prints that went out of the forest and across the upper intertidal zone to the most recent wrack line. The piles of tumbled rockweed might harbor small crustaceans, wayward seeds, or lost insects—all suitable for a snack. Another line of tracks went straight back into the shelter of the forest.

–Snowshoe hares had been busy in some areas. They too were looking for food, maybe willow or blueberry buds. But occasionally there were heavily trampled spots, very localized, as if there had been a dance or other social encounter. Popular routes became hare highways, packed flat along a small ridge or between two dense spruce stands.

–An otter had cruised for hundreds of yards along a frozen slough, making side excursions to visit (briefly) several beaver lodges. The deep trough left by its passage seldom came out in the open but usually stayed under the fringing conifers. Reaching the shore of a well-frozen lake, the otter abruptly turned around and went back the way it had come. The only open water on its route was a very small runnel below a beaver dam—a place not likely to hold good otter food.

–Across some thin pond ice, a great blue heron had gingerly minced its way from one patch of open water, at the inlet, to another, at the outlet. Taking very short strides on its long thin toes, it seemed to have been treading carefully. Little sticklebacks and juvenile coho, beware.

–In several places, we spotted narrow grooves on the snow surface, where a slim body had propelled itself on small feet. These wandering trails led to grassy tussocks, dove under logs, circled a pile of branches, disappeared under the snow and came out again. A mighty hunter was at work: a short-tailed weasel or ermine, whose coat turns white in winter, except for the tip of the tail. The short-legged, long body of a weasel is well-adapted for diving down vole tunnels and other tight places. However, that body form means that a weasel can’t afford to put on heavy layers of fat; the belly would drag when the weasel tried to run—not good for a hunter that has to keep moving for much of the day in search of prey. In addition to their small size, the body shape of weasels gives them a lot of surface area (where heat is lost) compared to the body volume (muscles and organs that generate heat), so they have a high metabolic rate to keep themselves warm. And that means they have to eat a lot. They eat mice and voles and small birds, and carrion when it’s available.

–Porcupines seem to wander widely, and we’ve found their trails in many places, often still distinguishable under a layer of new snow. One day we found a very fresh trail of footprints and even some quill-drag; we followed it along a little dirt bank until it disappeared over the edge. Looking down, we saw that a small log, sticking out parallel to the bank, had been wiped clean of new snow by the animal’s passage; the trail ended near the end of the log. Of course, we went around to an easier place to climb down the bank and investigated the trail’s end. There we found a deep burrow, with hairs and a few dried-up fecal pellets and a good barn-y smell, that ran into the bank for over two yards: a snug, dry den that had been used repeatedly for some time. Upon close inspection, that little access log had thousands of scratches, evidence of many balancing acts as the porcupine had ventured out and back.