Abstracts

Presented by Josh Ackerman - Email: jackerman@usgs.gov

California produces the majority of mallard and gadwall that are harvested within the state, and as such is an important breeding area within the Pacific Flyway. As part of the Suisun Marsh Waterfowl Program, we have assessed long-term trends in mallard, gadwall, and cinnamon teal breeding demography and factors influencing nest survival and nest density. Nest survival has fluctuated substantially among years and has trended lower in the past decade. Predation was the major cause of nest failure, with raccoons (53% of egg depredations) and skunks (27% of egg depredations) being the most predominant egg predators. Hens tended to select taller vegetation than was available within upland nesting fields, but nest vegetation height had little effect on nest survival. GPS-marked predators typically foraged along canal and wetland margins, and other edge habitats, indicating the increased potential for egg depredations in these areas. Temperature dataloggers placed within nests demonstrated that hens took 1-2 nest breaks per day, with the morning recess occurring around sunrise (5:00-6:00) and the afternoon recess occurring 1-5 hrs before sunset (16:00-19:00). Hens departed nest sites with their ducklings during daylight hours (98%), with 81% of broods departing the nest the day after eggs began to hatch and 53% of broods departing the nest within 14 hr after dawn. Duckling survival was relatively low and wetland salinity levels approached concentrations that have been shown to impair growth. These results have important implications for upland and wetland habitat management for breeding waterfowl.