Little winter puzzles

poop parties, shrew tracks, and muskeg mysteries

Early winter walks yielded some small puzzles for curious naturalists to contemplate. Here are a few of them.

Out at Eagle Beach, on a low tide, we observed many crows, mostly foraging busily. Along the tideline, they forage singly, each one slowly walking along the edge of the water, pecking at this and that, and occasionally winkling out something edible.

On top of the sandy berms lay a cap of fluffy snow, much marked by gull feet and the remains of the gulls’ dinners. On the ends of two of these berms, we saw tight clusters of crows, heads down, poking their beaks at something on the snow surface. When we went to inspect more closely, we found that blackish piles of shell fragments, regurgitated by the gulls, had been scattered as the crows sorted through the pile for bits the gulls might have missed. And most of the excreted yellowish splats of digested gull meals were missing their typical lump of solid waste. It seems that the crows had been dining on gull poop.

That seemed a bit strange, with all the small, intertidal animals that would be expected nearby. But the real puzzle was why the crows did this scavenging of gull ejects in gangs. The snowy berms were covered with evidence of gull presence, but the foraging gangs invariably gathered at one end of the berm, leaving the rest unscavenged. What’s the reason for these poop parties?

In a lovely muskeg we found a long trackway of a shrew. It had meandered for many yards on top of the snow, occasionally diving straight down and re-emerging from the same hole. Presumably it had sniffed out something potentially edible to fuel its constant search for more food. But why hunt on the surface of the snow, where the exposed position sees likely to increase the risk of predation?

Later, On Moose Lake, we found another long shrew trackway, extending for over a hundred yards over the snow-covered ice. This shrew periodically dove beneath the surface and came up a few inches farther on. Again, the shrew was travelling in a very exposed situation, and we wondered what made the risk worthwhile—perhaps a frozen insect or two, or some wind-wafted seeds, but what a dangerous place to look for them.

Plonking around on snowshoes in a muskeg, we noticed a small area in which several tiny shore pines had been mauled. The trees barely stuck up above the snow, but each of them had bent and broken twigs with abraded bark and one or two twigs from which the bark had been delicately peeled. No animal tracks were discernible near these mutilated tree-lets. Who was the culprit? ?A vole that tunneled up from under the snow??

That low-elevation muskeg on Douglas was quite familiar territory for me, but my companions wanted to go to the next higher one. So we thrashed through the blueberry tangles and wind-throws for a time that seemed longer than it really was. We didn’t find much sign of animal activity, but on our way back down, we noticed a huge, rounded boulder near the edge of the muskeg. It was snow-capped, but the sides were covered thickly with lichens, so it had been there a good while. We did a mental double-take and realized that we ‘never’ see boulders in muskegs. But why not? If we assume that trolls don’t make a habit of removing them, then what? The glaciers often left erratic boulders, but why don’t we see more of them in muskegs? Does the muskeg (technically a bog) just cover them up eventually? Then why is this boulder on the surface? Is there a rocky outcrop beneath it? I bet some scientist in Juneau can explain this!

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