Snow at last!

peripatetic mammals and birds, and a fungus attack

After a very dreary, dismal January, February produced some nice snow. Not enough, of course, and it didn’t last. But for a few days, snow made the daylight hours brighter and provided splendid opportunities for reading critter tracks. Here are some samples, along with ancillary observations.

A morning snowshoe walk at SAGA meadows, with fresh snow and partial sunshine was very productive. A river otter left its distinctive five-toed prints and sliding track all along the base of the ridge on the eastern side of the valley; it came from the Amalga area, heading to the saddle where the old horse tram crossed over to the Eagle-Herbert drainage. It’s a lot shorter to go by land than by sea (out around the Boy Scout beach to the mouth of the river), but we wondered why this individual chose to go by land. Maybe it likes sliding better than swimming? Long overland journeys are not unheard-of: we once tracked an otter from the Hilda Creek canyons up and over to the Fish Creek drainage near the start of the upper cross-country ski loop.

Red squirrels had been very active, making highways between brush piles and trees, and often diving under the snow, popping up several feet farther on. Under the snow there were a few little caverns whose floors were littered with the remnants of alder cones, where a squirrel had a picnic.

Snowshoe hares left their tracks especially under the drooping conifer branches. It was clear that hares had been munching twigs of highbush cranberry—small twigs of many bushes had been recently clipped and hare tracks nearby left no doubt about the clippers. Small well-trampled areas indicated a place, perhaps a latrine (?), where a hare had spent some time, but only a few of these had scattered pellets. We speculated that the hares might have re-ingested fresh pellets to extract more nutrients (a habit they share with many rodents).

A small bird—probably a junco—had hopped around under a low-hanging spruce branch and then flitted off, leaving short wing traces in the snow. A mouse or vole had travelled from one thicket to another, and some small rodent had nibbled the bark of tiny shore pines. A porcupine had wandered about before the last of the snow fell, leaving now-blurred but unmistakable traces of its passage. Near a small frozen slough, a mink or marten had walked over toward a tree; the prints were not clear enough for us to discern the subtle clues that might tell us which kind of beast it was and the trail was lost in a snowless patch under dense spruces.

A flock of red crossbills enlivened the morning, calling and flying from spruce-top to spruce-top, occasionally prying open a cone to extract the seeds. Did their messy feeding activities contribute to the fall of seeds we saw scattered on the snow or did the wind bring them all down?

We found good examples of the rough-bark fungus infection on alders, which featured in a recent essay. Some of the infected sites had been heavily used by sapsuckers, but these birds had been active in many places, leaving broad patches of their sap wells in the bark. Very young alders, still with their reddish bark, also showed signs of the fungus attack.

That was a good day, and so was the next one, when we snowshoed the upper loop at Eaglecrest. It was still snowing a bit up there, while the rain fell at lower elevations. Here, in addition to lots of squirrel tracks and those of a mouse, ptarmigan had been very busy, sometimes running across a wide open space, sometimes walking sedately from bush to bush. In one place we saw a pair of traces where ptarmigan had glided down onto the snow, wallowed forward for a few feet, and taken flight once more, leaving tell-tale depressions (from the jumping take-off) flanked by wing marks.

Crossbills nesting in winter

…here we go gathering twigs and moss…

Once again, this time in late February, the Auke Nu trail was in top shape, firm snow all the way to the cabin. As we sashayed along, I heard some soft and gentle warbling notes high in the canopy. I finally spotted some movement under a clump of moss that seemed to be growing on top of a witch’s broom (a parasite that distorts branch growth).

Underneath that clump of moss were three female red crossbills, busily selecting short twigs. They seemed to be the source of the songs I heard, although female crossbills don’t sing as much as males do. There is no indication in the literature that females sing a little song when gathering nest material. (But I’m tempted to suggest “Here we go gathering twigs and moss, twigs and moss, twigs and moss…”) I suppose it’s possible that some males were hanging around in the dense hemlock foliage nearby and providing the sound effects.

Crossbills often nest in loose clusters, several nests fairly close together. Females build the nests, although males may sometimes carry nest material. They can nest at virtually any time of year, even in the dead of winter. Nesting is initiated when females have enough food to develop eggs and can see that there’s lots of food still around for raising chicks. So when there is a big cone crop, as there is this year, they gear up for making babies.

Crossbills are nomadic, moving around from region to region, in search of good cone crops. If they find a really good one, they may stay and rear two or three or even four broods in one place. If not, they move on and rear a series of broods in different areas. Breeding is so tightly linked to food supply that young females only six months old can sometimes breed in a good cone year.

Even when the cone crop is good, things can still go awry. Crossbills are specialized to pry open cones and extract the seeds. They are most efficient at foraging from conifer cones and less efficient at eating other kinds of seeds. But if the air is dry for a period of time spruce and hemlock cones may open spontaneously and release the seeds to fly away on the wind. Dispersal of the seeds clearly reduces the availability of seed-laden cones for crossbills, but it allows the seeds a chance to escape seed predation by these birds and perhaps produce some seedlings.

As we walked along the trail, we noticed very localized patches where the ground was covered with tiny hemlock twigs and empty cones. We surmised that these patches were under trees where crossbills had been foraging. Crossbills often tear a cone off the branch, hold it in one foot, and pry out the seeds, letting the empty cone drop.

In addition to several groups of red crossbills, I heard what sounded like swarms of white-winged crossbills as we went up the hill (although one of Juneau’s ace birders says that one white-wing can sound like a whole bunch…). White-wings are probably nesting now too. Like the red crossbill, they are nomadic, can nest at any season if there’s a good cone crop, and often nest in clusters. Their breeding range goes as far north as the treeline but overlaps that of the red crossbill all across southern Canada and into the Rockies of the northern U.S.

White-winged crossbills male (L) and female (R). Photo by Bob Armstrong

Both species irrupt southward when cone crops fail in the north. Young crossbills and females are subordinate to older birds and males and are the first to feel the pinch of hunger. They often move well ahead of the dominants, leaving an area earlier and sometimes going farther south, almost to the Gulf coast. They seldom breed in the southern regions, however, and move north again in search of good cone crops.