Courtship display.
Within the last several decades, this species has adapted to nesting under manmade structures such as the Monterey Municipal Wharf where this photo was taken. Normally they nest in burrows in earth embankments. The species is largely a summer visitor and breeder in this area. They reverse the usual pattern of migratory birds in North America by wintering north, not south of their breeding grounds.
Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA |hand-held (no adapter)