Autumnal migration a sight to behold
One of the most fundamental wonders of birds is that they fly. We earthbound creatures plod along with heavy steps, and occasionally take off in our imaginations or machines. But birds do this effortlessly, and constantly fill the air around us. This is cause enough for inexhaustible excitement at the marvels of the world. But, those short and local flights that fall within our vision are just the smallest part of that airborne story. For many birds, those flights continue for hundreds and thousands of miles. And there is no better time to witness that immense, incredible phenomenon than at this moment, the height of fall migration.
Some fly by day, like raptors, swifts and swallows, because they can feedwhile they travel and findsafe roosts each evening.
The basic pattern is simple, although there are numerous variations. Even here in temperate California, more than half of the birds we see participate in a north-to-south migration. The great majority of our summer birds— dominated by insect-eaters like swallows, flycatchers and orioles — have already departed back to Mexico and Central America. Meanwhile, a wide variety of species that travel to our north for the breeding season are now beginning to arrive. First came the shorebirds, followed by waterfowl, raptors and songbirds.
Birds’ patterns and techniques of migration vary. Some fly by day, like raptors, swifts and swallows, because they can feed while they travel and find safe roosts each evening. Many songbirds, in contrast, fly by night and navigate by the stars or the Earth’s magnetic field, descending to find food during the day. Other birds make long, watery crossings that allow no stops at all. The bar-tailed godwit is one example that never fails to amazeme, flying 7,000 miles in a nonstop, seven- day
journey from Alaska to New Zealand with no rest, food or water.
Some birds we know personally are scarcely less impressive, like the rufous hummingbird whose last fall migrants pass through the Bay Area in September. Breeding in Canada and Alaska, they travel some 4,000 miles to Mexico on an energy reservoir contained within an eighth- of-an- ounce body.
Or consider our raptors, whose migration can be seen at Hawk Hill in the Marin Headlands as they are funneled over the Golden Gate. The most abundant bird at this count site is the turkey vulture, including both residents and long- distance migrants. I always admire their unflapping, efficient flight, and this is where they put that skill to its greatest test: in a month-long or longer journey from British Columbia to South America. As they approach the isthmus of Panama, the concentrating vultures far exceed the supply of carrion, and continue onward, fueled by wind and not by food. I love to watch them gliding southward on fall’s long and fasting flight, imagining that journey. This bird has seen the Andes.
Down on the ground, our winter songbirds are starting to arrive. The most noticeable of these around the neighborhood are undoubtedly our winter sparrows, especially the white-crowned and golden-crowned sparrows. These sturdy little flockers will grow to ubiquity over the course of October, until nearly every yard or weedy field hosts an everpresent smattering. You can hardly miss them if you have a feeder, whether seed or suet. And there is no bird sound I am asked about more often than the golden-crowned sparrow’s autumn song, a distinctive set of three descending whistles, sometimes likened to “oh, dear me” or “I’m so tired.” Now you will know it when you hear it.
There are other winter songbirds to seek in the coming months: kinglets, waxwings, thrushes and sapsuckers. My favorite of all is the Townsend’s warbler, a diminutive and quiet beauty that tracks down insects in the woods and discretely enters into neighborhoods. In the conifer forests where they nest, they live high and out of sight, foraging in the upper canopy. But in winter, these black and yellow apparitions descend into our latitudes and the elevations of our eyes.
The autumn woods are quieter than those of springtime’s chorus. But the leaves of bays and live oaks do not grow cold or wither. Concealed within its thick green fastness, new wings now start to murmur.
The autumn woods are quieter than those of springtime’s chorus. But the leaves of bays and live oaksdo not grow cold or wither.
Jack Gedney’s On the Wing runs every other Monday. He is a co-owner of Wild Birds Unlimited in Novato, leads walks and seminars on nature in Marin, and blogs at Nature In Novato. You can reach him at jack@ natureinnovato.com.