Degree

Doctor of Philosophy (PhD)

Department

Renewable Natural Resources

Document Type

Dissertation

Abstract

Mottled ducks are a resident species found in the southern United States that rely on coastal marsh and associated habitat to fulfill the needs of the entirety of their annual cycle. Population monitoring has revealed declines in western Gulf Coast (WGC) mottled ducks since 2008. Mottled duck populations are influenced by survival and recruitment, and changes in these factors may contribute to population declines. The overarching goal of this project was to identify the mechanisms potentially limiting WGC mottled ducks.

I captured adult female mottled ducks during molt on Rockefeller Wildlife Refuge and adjacent lands in southwestern Louisiana from 2017–2019. I marked 148 individuals with a backpack solar-powered GPS-GSM transmitter and monitored them throughout the year for mortality and nest attempts. I used a Known Fate model in Program MARK to determine annual and seasonal survival and how survival varied temporally and spatially. Mottled duck survival was best explained by maximum partitioning of the year by the hunted periods and biological seasons and the proportion of GPS locations in agricultural land. Annual survival in this study was 0.60–0.64, one of the highest estimates for WGC mottled ducks.

I identified 29 nest attempts during the breeding seasons 2018–2020. I used the nest survival model accessed through RMark to obtain daily survival rates of nests and evaluate the effect of local and landscape-level characteristics on survival. Nest survival varied positively with vegetation density. Lastly, I matched used nest sites with random locations within the home range of the female to examine nest site selection. Nest site selection varied by habitat type and vegetation density. Old fields were most likely to be selected, while emergent marsh was least likely to be selected. Probability of use also varied positively with vegetation density. During this study, survival estimates were similar to that of waterfowl species not experiencing declines and nest success and renesting propensity were relatively high. Nesting propensity was very low and future research should further investigate cues mottled ducks use to initiate nesting.

Date

7-3-2022

Committee Chair

Ringelman, Kevin M.

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