Parasitic Indicators of Foraging Strategies in Wading BIrds

Feeding ecology and trophic interactions of wading birds in southeast Florida were explored through a combined analysis of stable isotope profiles and endoparasite communities. Stable isotopes broadly characterize the feeding preferences of individual birds: stable carbon isotopes (δ ¹³ C) indicate the primary source of carbon in a food web and stable nitrogen isotopes (δ ¹⁵ N) correlates with trophic level. Parasite communities reflect long-term trends in diet, feeding ecology, movements and environmental changes. By characterizing the endoparasite fauna and combining it with stable isotope analysis, this project provides novel information on wading bird feeding ecologies and trophic interactions. We obtained deceased wading birds from South Florida wildlife rehabilitation organizations: green herons (n=9), great blue herons (n=29), great egrets (n=20), yellow-crowned night-herons (n=2), black-crowned night-herons (n=3) and white ibis (n=18). Three types of feathers, primary flight (n=16), retrices (tail; n=12) and contour feathers (n=8), as well as muscle, were analyzed for carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) stable isotopes. No significant difference exists between stable isotope values and feather type (ANOVA; δ ¹³ C: F (2,33), p=0.75; δ ¹⁵ N: F (2,33), p=0.85). Preliminary δ ¹³ C values for great egret feathers (n=18) range from -27.87 to -14.46‰ and range from -24.87 to -14.33‰ for muscle (n=11), which indicate the egrets are likely feeding from two different sources of carbon. Preliminary δ15N values range from 10.32 to 14.56‰ for feather and from 8.45 to 10.70‰ for muscle, signifying that the egrets are eating across one trophic level and keratinized feather is more enriched than muscle. This corresponds to other studies comparing muscle with keratinous tissues. Preliminary parasite identifications indicate that wading bird parasite communities are diverse and include at least 14 different species of digeneans and 5 different species of nematodes. Host and range extensions were noted for several parasite taxa. Broad, interspecific differences exist in parasite community structure. Preliminary analysis shows the great blue herons have the highest infection rate while the white ibis has the lowest. Internal parasite communities can be indicative of foraging habitat so the combined knowledge on trophic structure and ecological interactions will enable scientists and conservationists develop strategies for protecting bird populations and maintaining biodiversity.