Least Tern Return

California least tern. Photo by Jack Wolf, used under Creative Commons.

by Jody Zaitlin — published May 20, 2009

Every spring California least terns (Sternula antillarum brownie) return to the Bay Area to breed. The least is the smallest of all the terns, and they can be recognized by that small size and their white foreheads. They nest on sandy or gravely areas near good fishing spots. Unfortunately, humans have crowded them out of many beaches so their nesting sites are limited, and their continued survival is considered endangered. Fortunately, one of the most successful breading colonies in California is on Alameda Island at the former Naval Air Station. Other smaller nesting sites are sometimes used in Hayward and Pittsburg.

Access to the nesting site is restricted to prevent trampling of the eggs and chicks, but adult least terns can be seen foraging at various locations within 2 to 3 miles of the nesting sites usually between late April and late July. They feed on small elongated fish such as smelts and anchovies which they carry back to their chicks in their beaks. The birds spot their fish prey while in flight and then make dramatic plunges to the water's surface to catch them. Terns nesting on Alameda concentrate their foraging south of the Island, but you can also find them on the Emeryville and Oakland mudflats, and in the Oakland Estuary. When the young birds leave the nesting colony, they practice foraging in protected areas with calm water such as the salt ponds of the south bay.

All the terns leave the Bay Area in the late summer. Their wintering locations are actually unknown, but probably include the South American Pacific Coast.