September 16, 2010
I love the Fall Equinox (coming up on September 23). Equal day, and equal night. It’s the doorstep to cooler times, and more darkness—the introduction of upcoming Vampire Hours (riding to work in the morning darkness, riding home in the evening darkness). I really enjoy this time, but also the anticipation of winter riding. The bike gets outfitted with some extra lights (I even have a string of Christmas lights I rock for about two months), and I get to dust off my warming riding clothes.
I knew the Autumnal Equinox was approaching a couple of weeks ago because of something I’ve been observing and hearing on my bike commute: birds. You see, this time of year birds begin trickling south along the Pacific Flyway, or down and over from the Sierra, where they have been spending their summer. Not all birds migrate, of course, but many do. You see them in the spring, they’re gone for several months, and then they reappear in the fall as they head south to more tropical climates.
So, I’ve been seeing birds that have been gone for a while—some shorebirds and things like western tanagers—but I’ve also been hearing all birds perform what I’ll call the false spring sonata. The wrens, white-crowned and golden-crowned sparrows have been particularly vocal. Why? Songbirds are slaves to their hormones, hormones drive their singing, and those hormones are driven by the periodicity of the sun. As the days—and sunshine—increases in the spring, especially around the Spring Equinox, hormones increase and those little male songbirds just can’t help themselves and they sing all day long. The summer, of course, is busy with mating and raising their young, either here or farther north.
The Fall Equinox fools them. They sense that equal and equivalent amount of sun to darkness they experienced in the spring, their hormones kick in for a few weeks, and they start their spring ritual all over again, until a week or two after the fall equinox, and then they collectively call out “Doh!” Fooled. They chill, and settle in to their winter peregrinations or local routine.
Yep, you can figure that all out from the saddle of a commute bike. Now these guys, Canadian Geese, are interesting. Of course they don’t sing, only honk, but they do move around seasonally. Here in the SF Bay Area, there are resident populations, but seasonally you can also see their more wild relatives come winging in from the north, sometimes at night, honking in unison across the dark skies overhead.
Have you ever seen or heard a wedge of geese overhead at dusk or during the night?