Black Skimmers and Their Strange Bills Amaze Us

Last year I saw a single black skimmer, close to the shore, at Crab Cove and got so excited that I tripped in the sand and nearly did a head-dive—but I saved the camera and lens! Just needed to brush off the sand and get my focus aligned.

Skimmers occasionally can be found at Crab Cove and Elsie Roemer Bird Sanctuary, but they are seen more often at Shoreline Park in Mountain View and at Shell Bar in Foster City. They have also been reported at “Radio Beach,” the shoreline to the right of the toll booth on the Bay Bridge.

Black skimmers are in the family Laridae , which includes birds such as gulls and terns. In 1775, Carl Linnaeus gave them the binomial name of Rynchops niger ; loosely translated it means ‘beak face black,’ but in areas where they are found they are also called scissor-bill, scissor-beak, razorbill, cut-water, and seadog.  The seadog epithet is given for its dog-like barking or yipping.

The skimmer is the only bird with a lower jutting mandible, which gives its bill a unique look. The bill also causes the skimmer to catch food in an unusual way. It skims with its lower mandible in the water, closing the shorter upper mandible to catch any fish it finds. The bill’s two colors are also notable—red near the head and black on the tip of both upper and lower mandibles. Its tactile response must be super-fast to snag a fish while in non-stop flight. I’ve watched them catch fish as they skim and typically it is signaled by a quick upward snap of the neck and head as the mandibles close upon the prey.

The black skimmer’s eyes are also somewhat unique. While its pupils are large, its eyes often look like vertical slits, which may help when foraging at night or may soften the glare of sun reflected off the water.

The black skimmer is about 18 inches long with a 44-inch wingspan, and it weighs about 11 ounces, with the male larger than the female. The bird seems to create an optical illusion as is flies. Perhaps its streamlined body and long wingspan are deceiving but skimmers appear huge in flight!

Compare them to a Western gull at 2.2 pounds with a wingspan of 58 inches and you’ll see that skimmers are relatively small. While many of our common gulls are larger, among the terns only the Caspian Tern has a longer wingspan at 50 inches.

In Peterson’s third edition of Western Birds , published in 1990, the black skimmer is described as, “more slender than a gull, with extremely long wings.” It is not listed in Peterson’s second edition, published in 1961. Is this because the skimmer has gradually spread west and north from its earlier southeastern range? Sibley’s Field Guide reports, “flight also distinctive: graceful and buoyant, with slow beats of long broad wings.”

These birds are colonial coastal nesters, usually nesting on beaches, sandbars, shell banks, and islands. Like least terns and killdeer , they make a scrape in the sand to lay their eggs. Monogamous, both adults share incubating duties. Clutch size is one to five eggs, incubation is 21 to 25 days, and chicks begin to fly at around six weeks old, so adults spend at least 10 weeks raising their young.

As with all birds, black skimmer populations and distribution are negatively affected by loss of habitat, especially due to land development.  They are also sensitive to human intrusion and sea level rise due to global warming.

Describing the bird as “one of the most singularly endowed by nature,” John J. Audubon said, “the flight of the black skimmer is perhaps more elegant than that of any water bird with which I am acquainted.”  I have to agree. Watching a single skimmer is exciting; watching a flock bank and veer and wheel and swerve and bank again is exhilarating! It is truly a ballet that marries water with sky. As the famous biologist, Ed Ricketts, once said, “from the tide pools to the stars!” That sentiment is certainly applicable to black skimmers as they make the leap into the ether tangible and wondrous.

All in all, the skimmer is a unique bird with the lower jutting bill and vertical pupils, lowering its head and bill to the ground while resting, skimming the water’s surface for prey, and yapping or barking like a dog. A bird you can’t miss or ignore, entertaining in flight or at rest. We are fortunate that these beautiful birds are finding the Bay Area hospitable.

Rick Lewis is a long-time member of Golden Gate Bird Alliance and other environmental organizations. He contributes often to Bay Area and Central Valley birding groups that promote wildlife and habitat conservation.

This article is part of a series from the Friends of the Alameda Wildlife Reserve (FAWR), a Conservation Committee of the Golden Gate Bird Alliance (GGBA, formerly Audubon). Learn more about FAWR at www.goldengatebirds.org .

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