American White Pelicans foraging in Bodega Harbor, 19 May 2013
I like this picture because it reveals quite a bit about white pelicans.
About foraging — White pelicans often forage in groups. They feed by dipping their bills into shallow water, and often do so synchronously. Note the raised wing posture, which I'm guessing is for balance while reaching below the surface.
About habitat use — You can see that these pelicans are in a relatively sheltered location with mudflats in the background. Scanning carefully, you will also find strands of eelgrass draped around some of the birds (especially the second bird from the left), indicating use of seagrass beds.
About reproduction — Look closely for birds with gray feathers on their crowns. This coloration is found in chick-feeding adults. (White pelicans don't breed on the coast, but they've arrived here after nesting at inland lakes.) And the large rounded "horn" on the bill of some individuals is also only present during the breeding season (it's usually shed after eggs are laid).
About species interactions — Note the Great Egret in the background. The egret appeared to be "attending" this flock of pelicans, waiting for fish that the pelicans flushed or missed.