By Kathleen Brogan
While a November dip in the Bay may seem like a chilly idea to you and me, birds disagree. In fact, hundreds of thousands of migrate annually to winter in the temperate waters of the San Francisco Bay. Among their numbers is the Surf Scoter, who loves to dive hungrily into cresting waves in search of food.
“Skunk-headed coot” is not the most flattering nickname, but it aptly describes the distinctive white patches on the napes and foreheads of male surf scoters. The males’ entirely black body is accented by a colorful bill of orange, black, and white patches. Not as flashy, the females are brown and have slightly fainter white patches on their napes and foreheads. The legs and feet of males are a vivid orange, while those of females are yellow to brownish in color. Surf scoters love to duck and dive underwater, resurfacing only to rapidly fly away, wings humming.
Range and Habitat
Surf Scoters travel to the Bay all the way to from Alaska and Northwest Canadian territories where they live during warmer seasons. A favorite destination, the Bay Area hosts three-fourths of scoter species found in North America during the winter. Surf scoters prefer woods or tundra close to freshwater for their nests. Females aren’t too careful with their nests, and occasionally lose track of their eggs in the middle of crowded breeding grounds.
Surf scoters primarily eat mollusks and crustaceans, which they find by diving deep into the water. Strong swimmers, scoters can dive to depths of thirty feet. Because gulls like to pilfer the catches of surfacing ducks, scoters often dive in unison to avoid losing their meals. In addition to mollusks, scoters have developed a taste for herring roe laid on blades of eelgrass. Surf scoters can be found pulling out entire stalks of eelgrass by the roots to eat the delicate eggs.
Surf Scoter snacks have been severely contaminated. The majority of mollusks found in the bay contain high levels of mercury, selenium, and cadmium. Surface runoff near irrigation drains and old mines, when combined with discharge from oil refineries, spoil the homes and food of Bay Area birds. The Bay’s shifting ecosystem has invited invasive species, causing a change in prey-base for the Surf Scoter. In the 1980s, studies revealed that surf scoters found in the San Francisco Bay had higher mercury and selenium contents than any other species of waterfowl.
In November 2007, the Cosco Busan oil spill dumped over 50,000 gallons of toxic bunker fuel into the San Francisco Bay. An estimated minimum of 2,000 shorebirds were oiled and killed from the spill. Around 40 percent of the casualties were Surf Scoters. Although the species are not considered endangered, their population has declined about 50 to 70 percent within the last forty years.
Just this year, within a few weeks of the two year anniversary of the Cosco Busan oil spill, an oil tanker that was transferring fuel oil to a barge in the Bay spilled an estimated 400-800 gallons of oil into the surrounding waters. Thankfully, the Point Reyes’ Bird Observatory Oil Spill Response team acted quickly to rescue and rehabilitate the birds. They do not estimate that the number of avian casualties will be anywhere near that of 2007.