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Sightings in April

Posted: May 12, 2011 - 4:09pm
A porcupine feeds on cottonwood buds.    Photo by Bob Armstrong
Photo by Bob Armstrong
A porcupine feeds on cottonwood buds.

Near the start of the East Glacier Trail, a flurry of activity caught my eye. Creeping closer, I saw two male juncos in major conflict. Usually, male birds settle territorial border battles by visual displays and songs. But that wasn’t enough for these guys, who were going at it hammer and tongs. Fluttering up and down, chest to chest, pecking each other and buffeting with wings, until finally one rode the other down to the ground and held it there, whacking it for almost a minute (that’s a long time, if you are the whack-ee). Then they separated.

There may or may not be a repeat performance for those juncos. Sometimes one battle is enough to establish winner and loser. But not always. Several years ago, I watched two pairs of dippers on Salmon Creek, both pairs trying to nest less than 50 yards apart on a long cliff. This is way too close together for dippers, and they were at war with each other. I visited the area every few days, and the battles raged for at least two weeks, before one pair gave up and abandoned their nest site.

Out at Eagle Beach, there’s a big log whose roots are exposed to salt water and spray at high tides, and they seem to be wet most of the time. These roots hold a great fascination for pine siskins, red crossbills, and white-winged crossbills. Sometimes one can see all three species at the same time. The birds visit the wet roots regularly, and occasionally poke around in the seaweed below the roots, too.

All of the birds peck industriously at the soft, wet wood, seeming to pick up small green bits at times, but often what they pick up is invisibly small. The birds don’t carry their pickings back to a nest; they frequently fly to some nearby spruces and perch high in the treetops for a while, before returning to the wet roots.

This behavior is mysterious — what are they getting? And, what makes it so good that the birds return day after day over a span of weeks? One guess is that they are eating algae that grow on the surface of the wood, and in some cases they do seem to be pecking at green patches that get smaller as they peck. But the birds often probe into crevices worn into the wood, where algae may be unlikely. Another guess is that they are seeking salt from the soggy wood. But do these birds, which are known as seed-eaters, have an unusual craving for salt? We have yet to figure out why this root wad is so attractive.

Not very far away, in a tidal slough, pine siskins were busily nipping at a nearly submerged log and at the mud nearby. So, whatever it is, it is not something particular about the big log on the beach, but apparently something about wood wetted by salt water.

In the Amazon, seed-eating parrots commonly visit exposed clay banks and eat the clay, which helps neutralize the toxins that occur in the seeds of their diet. Could our birds be doing something similar?

On a sunny afternoon in late April, near Steep Creek, a friend and I watched a fat porcupine in the very top of a large cottonwood tree. It was foraging on flower buds, which would be opening in a week or so, when we hope to see bears beginning to do the same thing (but that’s another story!). The porcupine moved ev-er-so-slow-ly up a vertical branch, reaching out to pull in twigs and nip off the buds. Sometimes it would break off a twig, to bring the buds within reach. Then it crept backward down that branch, and bridged over to another one, with some difficulty: first the front feet, then — after several tries — one rear foot, then the other. And ev-er-so-slow-ly it climbed up the new branch. Sometimes it crept out on really small branches, so small that all four feet would have to be in a single line, with the bulky body balanced above. No wonder a major cause of porcupine death is falling out of trees!

After more than an hour, it slowly descended the trunk. The tail was clearly used as part of this procedure, tapping the trunk before the body moved, and tapping on branches that might be in the way. We surmised that it was feeling its way down. When it reached the ground, it trundled over to the creek, found a dead branch on which it crossed the water, and vanished into the forest.

• Mary F. Willson is a retired professor of ecology.

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