Tuesday, May 21, 2013

The Arctic Nearby


There is a conversion meteorologists use called the Adiabatic Lapse Rate. What it says is that for every thousand feet of gain in altitude the temperature drops three degrees Fahrenheit.  Biologists employ a corollary equating a thousand foot gain in altitude with 600 miles of latitude, meaning that going up a mountainside a thousand feet is the climatic equivalent of traveling 600 miles north. So if you are in Ohio or Virginia at an altitude of 700 feet above sea level and you drive to Cranberry Mountain in West Virginia -- at 3575 feet -- you barter a hundred-mile drive for a trip to the boreal forests of Canada, 1600 miles to the north. That's the theory and in practice it is probably not far off. 

One way to confirm the altitude-latitude conversion is to look at the range maps of some of the birds which journey from the tropics to breed in the boreal conifers. Many observe a breeding range across Canada from the approximate latitude of Hudson's Bay to the U.S. -Canada border, a clean and regular band -- except for a dangling appendix down the spine of the Appalachian Mountains. If we pick a couple of boreal breeders such as Northern Waterthrush and Mourning Warbler we see that their breeding ranges reflect this Appalachian peninsula. As a result, we in the eastern or mid-western U.S. can drive a relatively short distance into the Appalachian highlands and enjoy a fair chance of finding these two northerly warblers on their breeding grounds. Cranberry Glades 15 miles west of Marlinton, West Virginia is the place to do it.

Cranberry Glades are a relic of  the Wisconsin glaciation; they constitute a botanic community of reindeer moss and red spruce which developed when the wall of Wisconsin ice bulldozed northern Ohio and Pennsylvania, pushing an arctic climate into our now-balmy realm. The ice retreated but the altitude and boggy soils permit Cranberry Glades' boreal botany to persist in glorious isolation, ours to savor on a day's jaunt.

Of course, sorting through the birds' calls when we get there is another challenge. The attached video offers a comparison of the songs of Northern Waterthrush and Mourning Warbler filmed at the Glades this morning and to complete the confusion we add a shot of the Louisiana Waterthrush, a much more accessible bird breeding along wooded streams at the lower elevations most of us occupy. All three (they are all warblers) sing in a burst of whistles followed by a dropping inflection, and because we rarely get to see and hear the northern worthies, we might find it useful to make the comparison with our more familiar lowland waterthrush.

Caveat:  this video won't help a bit when you get to Cranberry Glades. If your experience is like mine the overlapping chorus of echos and harmonies will leave you befuddled. But go anyway to enjoy this tiny nugget of the north in our midst.

1 comment:

  1. Looks to me like: Birding "off" the Farm. Hope the place doesn't become as busy as Magee!
    Good work, Farm-boy.