Raptor-otica

Unless you're an avid birder or in kindergarten, the whole migration thing isn't exactly an academic turn-on. Ah, but then you've probably never been to Hawk Hill this time of year. And if you're still not interested, you're probably not a raptor geek. If you are, Hawk Hill is the most erotic biology field trip you'll ever take. Hawk Hill is the raptor geeks' porno convention, where we raptor groupies go to see Red-Tails, Coopers, Sharp-Shinned, Swainsons, Red-Shouldered, Broad-Winged, Kestrals, Peregrines, Merlins, and even Ferruginous Hawks, Rough-Legged Hawks, and the Golden Eagle, if we get lucky. Hawk Hill is the eastern facing promontory in the Marin Headlands at the north end of the Golden Gate Bridge. It offers a panoramic view of the Pacific, the Golden Gate, San Francisco Bay, and the Richardson Bay all the way over towards Berkeley and Oakland. It's where the Golden Gate Raptor Observatory conducts its raptor watch every year. For everyday raptor buffs with the right pair of binoculars, raptor-watch is a veritable skin-flick of raptor migratory behaviors. For the hundreds of volunteers who work in two-hour shifts counting the population of the raptor species that find their way to Hawk Hill, however, it is a serious empirical exercise. Raptors are a bellweather species. Since they are at the top of the food chain in their ecosystem, declines in their numbers can indicate problems within that ecosystem. What makes Marin the go-to peep-show for raptor counting?

By the time many raptors reach the Golden Gate Bridge, some of them have flown from as far as Alaska and Greenland, Tennessee and Virginia (banding programs tell us). Once they arrive, they suddenly stop at the Golden Gate and linger for long periods of time like tourists in the 70s who discovered our sensuous temperate weather and penchant for hot-tubs. But instead of hot-tubs, the warm thermals and updrafts on the wind-facing hills entice these birds of prey to join the big raptor orgy. Well, it may look that way, but something more amazing (and scientific) actually is going on. Embedded in North American raptors' genetic code is not only the instinct to migrate to the southern hemisphere, but an orientation for the only two ways to get there if they've never been before: the coasts. Juvenile raptors have no imprinted route south. But they know if they get to the coasts, it will lead them to where they need to go. Now, birds prefer to fly over land, which they can do most of the way. Problem is that little gap between Marin and San Francisco counties. That they don't like. So, it's not actually an orgy among the raptors at Hawk Hill; they're all hanging out on the thermals playing truth-or-dare to see who takes the leap over the gap. Most do, though some don't.

Next year, I get to join the banding program for the raptor observatory. But for now, because I'm not allowed to deflect my attentions outside the writing discipline, I am enjoying my own little hawk hill peep-show right here on the Corte Madera ridge. Today, I spotted two red-tailed hawks, a juvenile red-tail, and a cooper's hawk. Talk about a turn-on!