Few data are available on the use of seasonal, nontidal wetlands compared to tidal wetlands. Our study compared water-bird use of seasonal/nontidal, perennial/nontidal, and tidal wetlands in late April and early May on San Pablo Bay, California. Our study area was comprised primarily of formerly tidal wetlands, which were diked and some of which had developed seasonal wetland characteristics. Perennial/nontidal wetlands had been created on-site, and tidal wetlands were present bayward of the peripheral level. All four tidal and nontidal wetland types with low cover of open water and with corresponding high or moderate cover of emergent vegetation had little or no water-bird use. Mean water-bird use over the tidal cycle was highest for three of the five nontidal wetland types that had high cover of open water. Peak water-bird use (during some point in the tidal cycle) was highest for these three nontidal types and for tidal mudflats. Shorebird use patterns at the nontidal flooded field and the tidal mudflats were recipe cal, with the flooded field serving primarily as a high tide refuge and feeding area for birds that fed on the mudflats.
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