During winter, over 35,000 waterbirds, along with tens of thousands of shorebirds and gulls, pack the surface waters of Tomales Bay. This extraordinary phenomenon led, in 2002, to global recognition of Tomales Bay as a Ramsar Wetland of International Importance.
For three decades ACR has tracked the abundances of nearly 60 species of loons, grebes, cormorants, ducks and other waterbirds in the bay. These studies have revealed patterns of winter population growth and decline that are complicated enough to seem mysterious.
A magnet for herring spawning
Beneath the surface, tens of millions of Pacific herring (Clupea pallasii) also enter the bay each winter, to spawn in the vast, subtidal meadows of eelgrass. These events precipitate spectacular waterbird feeding...