Gettysburg

Great ride yesterday, including 10 miles of rail trail. Three states in one day, though to be fair, Robert E. Lee put more miles into PA, and I only squeaked into WV by the width of the Potomac.

Bicycling enables me to see slo-mo changes in bird distribution as I travel across the landscape. Crossing the Mason-Dixon into Maryland prompted me to think of several other boundaries.

Black Vulture, Hawk Mountain

New Hampshire is Turkey Vulture country. Black Vultures reach the northern limit of their range in northern New England. They do better in a hot climate in part because they have a heavier body relative to surface wing area, which means it takes more thermal activity to keep them in the air. As I peddle toward the south, they are becoming much more common.

I crossed another boundary yesterday – the line that separates Black-capped Chickadee from Carolina Chickadee. Almost indistinguishable, they are best identified by range. Black-capped Chickadee is a familiar bird at my backyard feeders in New Hampshire. Carolina Chickadee is a southern species whose range extends north to southern PA. Though their song is different, their calls are similar. However, I have a good ear, and yesterday for the first time I began to notice changes in the chickadee sounds emanating from the forest. I had entered Carolina Chickadee country. The zone of overlap, where both species interbreed, has been shifting northward at about 0.7 miles per year, and now reaches north of Hawk Mountain. Because Carolina Chickadees are the warm weather chickadee, climate change is thought to be the reason for the shift.

I have also noticed an uptick in opossums as measured by roadkill. Opossums originated in South America and came north during the Great American Interchange about 3 million years ago. They are not cut out for New England winters. Meade Cadot at the Harris Center tells me that it is not uncommon to see individuals in New Hampshire with frostbit ears and tails.

Oh, and Arsenal beat Chelsea!!!