An informative sign told that the whole 2-mile stretch I'd just walked plus the next several miles of airport and industrial area had once been a vast tidal marsh, now mostly drained and "developed". But one patch does remain right where the trail is interrupted at the south end of the airport and stretching in an arc from the trail to the runway. There were thousands of birds resting in shallows and on saltgrass-overgrown shores, some of them near enough the trails for good photographs, in spite of the fog. Here: Willets, American Avocets, Northern Shoveler. Just a small handful of the vast flocks of these and other species standing further out.