Audubon Canyon Ranch has monitored shorebird populations (Scolopacidae and Charadriidae) on Tomales Bay since 1988. I examined ten years of shorebird monitoring data for population trends and shifts in local foraging distributions, and related these patterns to flock movements, populations, and variations in weather. We conducted eight baywide counts of shorebirds each year and estimated early winter and late winter population levels. During each baywide count, the bay was subdivided into 10 standard count areas covered simultaneously in 60-90 minutes by teams of qualified volunteer observers. All counts began when the rising tide was approximately 0.76 m above MLLW at Blake's Landing. To further investigate the relative influences of weather and food availability on wintering shorebirds, I conducted mass balance trials on Dunlin in an outdoor aviary. I measured daily changes in energy intake, body mass, and thermal metabolic costs, and analyzed patterns of energy use in relation to variations in weather and food availability, and compared these patterns to shifts in winter habitat use.