Along with changing leaves, cooler weather, and pumpkin spice everything, one of the most exciting signs of autumn is the hundreds of thousands of birds that flock to our Bay shorelines. The Bay Area is a prominent feeding area along the Pacific Flyway, a major migration route stretching from the Arctic to South America. About one million birds live or winter around the Bay during migration each year, making it the most important habitat on the west coast for migrating shorebirds. As such, it has been designated as an Important Bird Area by the National Audobon Society and the American Bird Conservancy.
Northern environments such as the Arctic, Canada, and northern prairie offer better breeding opportunities for these birds in the summer: a seasonally abundant food supply, fewer predators and parasites than southern climates, and longer days for foraging. But in the winter, those regions are frozen in snow and ice, covering seed crops and insects and rendering the environment too harsh for survival. As a result, instinct drives migratory shorebirds to undertake an incredible journey–up to 15,000 miles long–twice each year.
As the Arctic days grow shorter, hormones trigger increased food consumption and fat storage, and the restless urge to migrate. At the outset of migration, up to 50% of the birds’ body weight may be fat, which they will lose almost entirely during the long flight. The birds navigate using a combination of directional clues: the earth’s magnetic field, the sun, and the stars. They fly at speeds around 50 miles per hour at altitudes up to 10,000 feet. Juveniles usually migrate without the help of experienced adults, indicating the flight pattern must be genetically programmed.
Here are a just few shorebird species found in our region–keep an eye out for these seasonal guests, and wish them well in their long, difficult travels!
Long- and Short*-Billed Dowitchers (Limnodromus genus): Dowitchers are characterized by their long, straight bill, and a white wedge visible on their back when in flight. They feed on invertebrates in the mud by using their bills in a motion similar to a sewing machine.
Killdeer (Charadrius vociferus): The “broken wing act” is a unique behavior to the killdeer, designed to distract predators from its young. While the chicks freeze, the parent flops around, feigning injury, to draw the predator toward it–then, as the predator approaches, the parent suddenly recovers and flies off. The killdeer has a distinctive appearance as well: red-ringed eyes, and two black bands around its neck and breast.
Willet (Catoptrophorus semipalmatus): The willet’s outer plumage is a dull gray-brown, but it displays a bold black and white wing-pattern while in flight. Its call sounds similar to its name: “Willet, willet.”
Long-Billed Curlew (Numenius americanus)*: The curlew is the largest shorebird in North America, with a long (seven-inch) curved bill for probing, allowing it to reach prey unavailable to other shorebirds.
Ridgway’s (formerly Clapper) Rail (Rallus obsoletus)*: Ridgway’s Rail is a rare salt marsh resident, endangered due to habitat encroachment and introduction of the nonnative red fox.
Plovers (Charadrius and Pluvialis genuses)*: Plovers are small, plump birds with short beaks and long legs. They hunt by sight, rather than feel, as probing shorebirds do. The snowy plover, an endangered species, breeds locally, making the Bay Area a high priority region for conservation.
Sandpipers (Calidris genus)*: Similar to plovers, but with longer beaks, sandpipers include the wave-chasing sanderlings, made famous by the Pixar short film “Piper.” The smallest sandpipers are referred to as “peeps” after the sounds they make.
Whimbrel (Numenius phaeopus): The whimbrel is a large shorebird, with several distinctive features: a striped brown and white head, a long, curved bill, and dark legs.
Black-necked stilt (Himantopus mexicanus)*: The Black-Necked Stilt has a distinctive black and white body with bright red legs. In proportion to its body, the stilt has the longest legs of any North American shorebird.
*Indicates an Audobon Society Priority Bird