Wetland Availability and Salinity Concentrations for Breeding Waterfowl in Suisun Marsh, California

Availability of wetlands with low salinities during the breeding season can influence waterfowl reproductive success and population recruitment. Salinities as 2 ppt (3.6 mScm–1) impair duckling growth behavior, mortality occurring above 9 (14.8 mScm–1). We used satellite imagery to quantify amount available water, sampled surface water salinity at Grizzly Island, in brackish Suisun Marsh, three time-periods (April, May, July) over 4 years (2016–2019). More was lower wetter (2017, 2019) than drier (2016, 2018), decreased 73%–86% from April July. Across all years, majority (64%–100%) wetland habitat area had what has been shown negatively affect ducklings (> ppt), up 42% associated ppt). During peak production 81%–95% ppt, 5%–21% ppt. In May driest year (2016), only 0.5 km2 low-salinity (< ppt) study area, compared 2.6 wettest (2017). Private duck clubs own Island consistently a greater percentage land flooded summer did publicly owned wetlands, but private generally higher public likely because they draw higher-salinity sources. By July, few remained flooded, most high enough survival. Local populations would benefit management practices that provide fresher retain more through