Parasitic Indicators of Foraging Strategies in Wading Birds Sarah Gumbleton Nova Southeastern University, [email protected]
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Nova Southeastern University NSUWorks HCNSO Student Theses and Dissertations HCNSO Student Work 7-24-2018 Parasitic Indicators of Foraging Strategies in Wading Birds Sarah Gumbleton Nova Southeastern University, [email protected] Follow this and additional works at: https://nsuworks.nova.edu/occ_stuetd Part of the Marine Biology Commons, and the Ornithology Commons Share Feedback About This Item NSUWorks Citation Sarah Gumbleton. 2018. Parasitic Indicators of Foraging Strategies in Wading Birds. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (484) https://nsuworks.nova.edu/occ_stuetd/484. This Thesis is brought to you by the HCNSO Student Work at NSUWorks. It has been accepted for inclusion in HCNSO Student Theses and Dissertations by an authorized administrator of NSUWorks. For more information, please contact [email protected]. Thesis of Sarah Gumbleton Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science M.S. Marine Biology Nova Southeastern University Halmos College of Natural Sciences and Oceanography July 2018 Approved: Thesis Committee Major Professor: Amy C. Hirons Committee Member: David W. Kerstetter Committee Member: Christopher A. Blanar This thesis is available at NSUWorks: https://nsuworks.nova.edu/occ_stuetd/484 Nova Southeastern University Halmos College of Natural Sciences and Oceanography Parasitic Indicators of Foraging Strategies in Wading Birds By Sarah Gumbleton Submitted to the Faculty of Nova Southeastern University Halmos College of Natural Sciences and Oceanography In partial fulfillment of the requirements for the degree of Masters of Science with a specialty in: Marine Biology August 2018 Acknowledgements Many thanks to my committee members, Drs. Amy C. Hirons, Christopher Blanar and David Kerstetter for all their extensive support and guidance during this project. Thanks to the lab members and volunteers, especially Jennifer Coley, Ashley Nakata, Rachael Stevenson, and Erin Smith, of the Fisheries Lab and the Charismatic Megafauna and Oceanography Lab for their assistance in bird dissections, lab processing, and field sample collection. A special thanks to Caitlyn Nay, Michael Nakama, and Brittney White for sharing their knowledge on birds and parasites. I would also like to extend my gratitude to Dr. Christine France from the Smithsonian Institute for analyzing stable isotope samples. Lastly, thanks to my family, especially my parents and brother, and friends who have supported me during my Master’s degree. The field component of this project was made possible by funding awarded by the Southern Florida Chapter of the Explorers Club Research Grant. 2 Abstract Feeding ecology and trophic interactions of six species of wading birds were explored through a combined analysis of stable isotope profiles and endoparasite communities. Stable isotopes broadly characterize the feeding preferences and geographic information, while parasite communities reflect long-term trends in feeding ecology. Deceased birds were obtained from four South Florida wildlife rehabilitation organizations. Of the 81 birds dissected, 73 contained parasites. Parasites were predominately found within the gastrointestinal tract. Host and range extensions were noted for several parasite taxa. Bird host species had a significant effect on the parasite community (P=0.001) while wildlife center location and maturity status did not. Stable nitrogen (δ15N) values for pectoral muscle tissues, representing approximately 24 days, ranged from 6.44 to 13.48‰ while stable carbon (δ13C) values ranged from -33.39 to - 11.66‰. δ13C varied significantly among location (P=0.0002) and δ15N varied significantly among species (P<0.0001). When δ15N and δ13C was analyzed in combination; bird species (P=0.001) and location (P=0.001) were significantly different. By using this combined approach of stable isotope analysis and parasite identification, it was possible to elucidate more components of bird feeding ecology. Stable isotope analysis provided knowledge on trophic interactions based on δ15N values, while δ13C was used to determine the differences in geographic foraging location. As endoparasites are acquired trophically via food-web interactions, identifying the parasite community allowed for trophic links to be drawn between organisms present within the same environment. Combining these two techniques allows for an abundance of information on feeding ecology and trophic interactions to be obtained. Keywords: Ardeidae, Threskiornithidae, parasites, stable isotopes, δ15N, δ13C 3 Table of Contents Acknowledgments Abstract Introduction Wading Birds Study Species Parasite Interactions Stable Isotope Analysis Carbon Isotope Ratios Nitrogen Isotope Ratios Stable Isotopes in Birds Materials and Methods Permits Field Collection Laboratory Processing Bird Processing Parasite Analysis Stable Isotope Analysis Statistical Analysis Results Specimen Collection Parasite Data Stable Isotope Data Discussion Parasites Diet Wading Birds Conclusion Literature Cited Appendix 1: Dietary items of wading bird species Appendix 2: Host morphometrics Appendix 3: Endoparasite descriptions Appendix 4: Endoparasites previously reported in wading birds 4 List of Figures Figure 1. Map of wildlife centers and sampling locations Figure 2. Non-metric multidimensional scaling of parasite community and wading bird species Figure 3. Cluster analysis of parasite communities Figure 4. Shade plot and cluster analysis of parasite communities and wading bird species Figure 5. Principal component analysis of stable isotope ratios and wading bird species Figure 6. Stable carbon and nitrogen isotope ratios for six species of wading birds Figure 7. Stable isotope ratios for wading bird species and wildlife center location Figure 8. Stable isotope ratios for potential prey items and sampling location Figure 9. Stable isotope ratios for species of wading birds and species of potential prey items 5 List of Tables Table 1. Dietary preferences of six wading bird species Table 2. Wading bird specimens collected from wildlife rehabilitation centers Table 3. Parasite prevalence and species richness for wading bird species Table 4. δ15N and δ13C of muscle tissue of 81 individual wading birds Table 5. δ15N and δ13C of 146 representative prey samples 6 Introduction The landscape of South Florida is a continually changing environment. Coastal zones are under increasing pressure due to urban developments, which in most cases are established on wading bird habitats. Wading birds are critical contributors to ecological function, driving energy flow within ecosystems via predator-prey interactions and mediating energy flow between terrestrial and aquatic habitats (Polis and Hurd 1996; Mallory et al. 2010). The feeding ecology, trophic interactions, and movements of these species are of significant interest in terms of understanding local ecology and in predicting the effects of coastal development and habitat alteration of these important species. Due to these inherent ecological linkages, wading birds can be thought of as sentinel species that indicate the ecological health of coastal habitats (Mallory et al. 2010). Particularly in South Florida, wading birds can be found in habitats ranging from the freshwater marshes in the Everglades to the saltwater mangals of the Florida Keys and can therefore provide valuable environmental information across a wide geographic scope. Through a combined analysis of stable isotope profiles and endoparasite communities, the feeding ecologies and trophic interactions of six species of wading birds were investigated. Stable isotopes were used to broadly characterize the feeding preferences of individual birds. Parasite communities are reflective of long-term trends in diet, feeding ecology, movements, and environmental changes. It is difficult to track and measure the diets of wading birds using conventional approaches such as forced regurgitations, live observations, or post mortem stomach content analysis, which only provide a snapshot of an individual’s diet (Marcogliese and Cone 1997; Inger and Bearhop 2008). By using stable isotope analysis in combination with characterization of the endoparasite community, it is possible to obtain dietary information over longer periods of time. Wading Birds The wading birds utilized in this study are from two families within the order Pelecaniformes: Family Ardeidae contains the herons, night herons, and egrets, while Family Threskiornithidae includes the ibisis. There is little to no sexual dimorphism with 7 these species. Birds within these families are long-legged, often have long necks, and are adapted for wading in shallow-water habitats to capture animal prey. Wading birds feed on a variety of food including other birds (particularly chicks), small mammals, and a range of aquatic food items including fish, amphibians, and invertebrates (Table 1; Appendix 1). The majority of these birds are associated with aquatic habitats that range from frehswater marshes and meadows to the shores of marine environments, including mangrove mangals (Brooke and Birkhead 1991; Schreiber and Burger 2001; Lovette and Fitzpatrick 2016). Study Species Birds in Ardeidae have straight, harpoon-like bills and narrow heads. They also have a modification to their sixth cervical vertebrae, which allows their long necks to be held in an S-shape while in flight (Brooke and Birkhead 1991; Schreiber and Burger 2001). Most species feed in or along the water and use their dagger-like bills