Black Skimmers of Foster City

Reminiscent of a large, bizarre-looking tern, Black Skimmers (Rynchops niger) are one of those really neat, must-see species any birder should have on his or her list.  Their black-white-and-red coloring is as striking and attention-grabbing as their uniquely-formed bill.


Skimmers are in the same family as terns and gulls (Laridae), and last weekend, the flock we saw along the San Francisco Bay in Foster City was happily sharing its sand spit with numerous Ring-billed Gulls and Forsters Terns (not to mention hundreds of sandpipers and plovers, among others).


The laterally compressed bill of the Black Skimmer appears thick and bulky from the side, but is knife-thin when viewed from the front.  The lower mandible protrudes farther than the upper, giving the birds the appearance of an under bite.  This special design allows skimmers to literally plough through the water as the bird flies low over the surface, its bill open, lower mandible slicing through the water.  As the bird skims along the top of the water, contact with prey causes the upper bill to snap shut when a fish has been caught. 


In addition to possessing bills with unusual proportions, Black Skimmers are recognized at a glance in flight by their extremely long, thin wings, and on land by their short red legs.  Flocks of Black Skimmers often fly in formation, turning and maneuvering through the air in unison, even beating their wings in synchronization.


Black Skimmers prefer sheltered coastal waters, such as sheltered bays, lagoons and estuaries, but may also be found inland at the Salton Sea in Southern California.  Flocks are often seen resting on sandbars, as well as gravel or shell bars, and open beaches with little vegetation.  Along the central coast of California, Black Skimmers are regularly seen in the shell bar area of Foster City, along the western side of the San Francisco Bay, and occasionally farther south in the area of the Moss Landing harbor. 

Black Skimmers nest in large colonies, often mixed with species of terns and gulls.  Nesting sites include sandy islands, shell bars and beaches, and nests are little more than shallow depressions in the ground.  Because Black Skimmers nest very close to the water's edge and feed along the surface, they are one of the species that is the most negatively effected by oil spills.

Watch the video below, from the Cornell Lab of Ornithology, to see the interactions between Black Skimmer parents and chicks!


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