Piscivorous avian species are of particular importance in Mississippi due to their depredation of cultured catfish throughout the states aquaculture industry. The three most common of these species include the double-crested cormorant (Phalacrocorax auritus), great blue heron (Ardea herodias), and great egret (Ardea alba). Information on these species aquaculture use can aid in effective and ethical management while also providing insight into their foraging ecology and habitat use, which is particularly important given these species augment their nutritional requirements using man-made food sources. The objectives of this research were to explore numerous aspects of avian foraging ecology in relation to aquaculture at multiple spatial and temporal scales using historic and contemporary aerial survey data. First, we examined the distribution and abundance of species on aquaculture at both the farm and pond scale. Pond contents and characteristics influenced each species, including culture practices and surroundings. In all cases, the amount of aquaculture was positively related to species abundances. Pond and farm selection relationships were species-specific, illustrating inherent differences in their foraging ecology. Consequently, specific management actions will depend on the targeted species. We also found cormorant densities on aquaculture has not changed in the past 15 years, even though aquaculture has significantly declined. Second, we measured cormorant distribution between aquaculture and natural water bodies. The highest use of aquaculture occurred when producers were not allowed to use lethal control, whereas the lowest use occurred when producers could. This trend highlights the potential influence of mortality risk on cormorants' foraging distribution. Lastly, we examined cormorant dynamics at the regional scale using roosting data. We found the Midwest breeding population of cormorants has been increasing, but the abundance of cormorants wintering in Mississippi has been decreasing, suggesting aquaculture is the primary cause of inhabitation of the state. We also found the phenology of cormorant spring migration is occurring earlier each year. Aquaculture area had a positive influence on cormorant distribution at roosts particularly prior to migration. These findings suggest changes in agriculture, and potentially climate change, can influence phenology, distribution, and abundance of avian species at multiple scales.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-3969 |
| Date | 09 August 2019 |
| Creators | Burr, Paul |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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