The vanishing act

Black angus cattle at sunset

Barn swallows are gathering on the wires along the old snowmaking pond. Soon they will be gone, headed south for another season. One morning they will be there, lined up like clothespins on a line, but when I return to the cabin in the evening they will be gone, all at once.

Not many species of birds migrate in this all or nothing pattern. Most have a window of migration peculiar to that species. Some of the windows are early in the season, others as late as the first snow. A flurry of activity usually accompanies the first decent frost, as though they need that reminder to get themselves airborne. Some of the migration windows are pretty tight, lasting for just a week or so; others stretch out over the entire fall.

Swallows all leave here on the same day, though I often see the more northerly birds still heading south when I am sitting on a hawkwatch in early September. The day the barn swallows leave Roundtop varies by just a day or so each year. Likely weather plays a part. Most commonly they will be gone on the 26th or 27th of August.

At this point, just under two weeks before they head south, they start to gather on the wires in the evenings, a few or several more each night until the day comes when they all vanish. Other summer species are still on the mountain and will be for a while yet. I still hear the pewee’s haunting echo in the early morning or after sunset.

Migrating shorebirds will sometimes stop to spend an hour or a night on the mountain. I never see many of them, and none ever stay very long. This area has plenty of other spots more suited to shorebirds—the Susquehanna River, the bigger lake at Pinchot, to name just two. I’ve often wondered why even the few I do see stop here when those other, better sites should be visible to an airborne bird that chooses instead to land at a small pond atop a mountain. Are they so exhausted from a long day’s flight that they can’t fly for another 5-10 minutes? They rarely appear that way. Maybe they think the ponds will prove a bonanza for a single, hungry shorebird. Their stopping here is a mystery all their own, a secret I can never penetrate.

Perhaps that’s part of why I enjoy migration so much. It’s a visible rendering of one of the world’s best mysteries. Each year, scientists uncover a bit more of the mystery, though that doesn’t diminish it. If anything, the explanations make the mystery all the deeper and that much sweeter. One of nature’s most awe-inspiring events happens right over our heads, twice each year.