<p> There are five subspecies of Black-necked Stilts (<i>Himantopus himantopus</i>). The American Ornithologists' Union calls the American version <i>Himantopus mexicanus</i> and internationally it is called <i>Himantopus himantopus mexicanus</i>. </p> <p> Black-necked Stilts are found in North and South America. They are fairly common in the San Francisco Bay Area where they breed. </p> <p> Sexes are similar but females are recognizable because their backs are brownish instead of black. Black-necked Stilts will flock together except when roosting. Then they spread out. They work together to discourage predators. </p>