Migrating Hawks- September
There is a mass movement under way. It’s all around you. It’s in the park, it’s over your head, it’s past your car, and it’s in the tree right outside your bedroom window. It’s a movement invisible to most people. It is the quiet flow of birds. Right now there are millions of warblers, shorebirds, finches, swallows, and nuthatches migrating south past us. As the days shorten and the food supply dwindles birds travel to more hospitable climes.
The most exciting, the largest and certainly the easiest to see of all these migrating birds are the hawks, the birds of prey, and the raptors. And this week is the peak of the hawk migration.
We’re fortunate here in the Bay area to live near one of the easiest places to see this event. You know the place; it’s the highest point along the Marin Headlands where all the car commercials are shot. The United States Army named it Hill 129 (how romantic) but we now call it Hawk Hill. Currently there are between 100 and 150 hawks darting across to San Francisco. This is the greatest concentration of hawks in the entire West.
But why do the hawks gather at this particular spot? As the hawks move south by the coast and along the inner Coast Range they encounter San Francisco Bay. Hawks are reluctant to cross over the open water. You might say to yourself “What are they scared of? They can fly. What’s the big deal?” Of course, it is true that they can fly but hawks take advantage of thermals- hot air masses that rise above the land–for additional lift. And above a cool body of water like San Francisco Bay not only are there no thermals, but also there tend to be downdrafts. It is harder and takes more energy to fly across water.
Therefore the hawks move along the edge of the Bay and are slowly funneled westward until they come to the very narrowest part—that short bottleneck of open water called the Golden Gate. Above Hawk Hill the birds gather; they soar around and around. It is tempting to get anthropomorphic because it seems as if the birds
are working up their courage. “Just one more circle and then I’ll do it…ahhggg maybe next time.” After shooting across the Gate the hawks continue south. Some will find central California a great place to winter, but many continue on to Mexico and even South America.
Nineteen different kinds of hawks pass over the golden gate every autumn. Several years ago observers recorded sixteen species in a single day! Right now the dedicated watcher could easily expect to see ten species of raptors in an afternoon of viewing at Hawk
Hill. The most common are red-tail hawks followed by Coopers or sharp-shinned hawks, turkey vultures (actually a falcon relative), northern harriers, black-shouldered kites, red-shouldered hawks and broad-winged hawks. The remaining ones are rarities such as prairie falcons, merlins, golden eagles, and rough-legged hawks.
I strongly suggest that choose a fogless day, grab your binoculars and head to the Headlands. The Golden Gate Raptor Observatory has volunteers–Hawk Watchers– stationed on Hawk Mountain every day from 10- 4. These volunteers identify and count the hawks passing by. They are more than happy to answer your questions.
But if you happen to miss the peak this week don’t be dismayed, the hawks will continue in good numbers through the month of October. The broad-winged hawks are just now arriving.