Abstracts

Presented by Jacqueline Satter - Email: jmsatter@ucdavis.edu

The Suisun Marsh is an estuarine system adjacent to the San Francisco Bay at the confluence of rivers that drain Californias Central Valley. Historically, it supported large numbers of wintering waterfowl with current peak counts approaching 60,000. Despite high historic use of Suisun, current use by dabbling ducks has been in decline the past several decades. To better understand these declines, we conducted a comprehensive study focusing on diet preferences and corresponding body condition of seven common species of dabbling ducks in the Suisun Marsh during two winters: 2017-2018 and 2018-2019. We investigated how body condition and diet differ between species, between sexes, and across the wintering season from October to March. Diet samples were obtained by removing and analyzing contents of esophagi from hunter-donated samples (n=500, 2017-2018) and collection by pass shooting (n=700, 2017-2018 and 2018-2019). The collected specimens were extensively measured, necropsied, and homogenized. Aliquots of homogenate were sent to the UC Davis analytics lab for proximate analysis, focusing on lipid content as an index for body condition. Our study will provide insight into current food selection, food preference, and nutritional shifts of dabbling ducks in the Suisun Marsh, and will indicate how diet and nutrition relate to overall body condition across winter. We are also comparing contemporary diets of three species to corresponding historical diet data collected in the Suisun Marsh 20 years ago to examine shifts in diets over the past two decades. Current dietary preferences will inform habitat management of specific food plant species needed to support the current and targeted populations of waterfowl in this important wetland region of California.