Large numbers of Elegant Terns have arrived in our Richardson Bay Audubon Sanctuary over the last week. On Monday, an estimated 400 were seen roosting and foraging over the bay; nearly 200 of these were observed resting on Aramburu Island’s new shoreline.

Elegant Terns do not breed in the Bay Area. More than 95% of their entire population breeds on one small island in the Sea of Cortez (Isla Rasa). Adults usually lay just one egg, and once the young have fledged, they move north along the California coast where the fledglings learn to forage on their own, taking advantage of schooling anchovies and other small fish. They usually arrive in the Bay Area sometime in June and stay through late October/early November, when they head again to southern South America for the winter. Young remain relatively dependent on adults often for more than six months after fledging.

In Richardson Bay, up to 700 have been observed at once—which is approximately 1% of the estimated global populations—but prior to the 2012 Aramburu shoreline reconstruction there were very few sightings of terns using the island. Starting in the late summer of 2013, they roosted on the island’s new beaches in the hundreds. In fact, on August 16, 2013, we counted nearly 400 on Aramburu Island alone.

Peak numbers are expected to occur in September, making it a great month to visit the Richardson Bay Audubon Center & Sanctuary for some birding.