A diet analysis was conducted on twenty-two Sacred Ibis, Threskiornis aethiopicus, a non-native wading bird in southeastern Florida. It is believed that anthropogenic diet resources have provided sustenance to this population (N=73), and has allowed this species to flourish. The establishment of this large wading bird would presumably put pressure on the larger bodied endangered Wood Stork, Mycteria americana, and the smaller bodied White Ibis, Eudocimus albus, through chick predation and resource competition. Twenty-two Sacred Ibis carcasses were acquired from the U.S. Department of Agriculture Wildlife Services in 2008, collected as part of an eradication program. Morphometric data, the first such data for this species in North America, was obtained for 8 adult males and 5 adult females, and is included as an appendix. The contents of the esophageal tract and gizzards were used to classify ibis diets as being of anthropogenic origin if they contained: cheese, meat, paper pulp, and/or pellet meal.
Results/Conclusions
We found the diet composition is represented predominately by food items that represent an anthropogenic resource (58% of the cumulative biomass). Ibis utilizing anthropogenic resources had a greater gut-content biomass (26.99g ± SE 5.35g) than birds utilizing natural resources (8.74g ± SE 2.21g) [H = 8.05, d.f. = 1, p < 0.01]. Natural diets, on average, contained a significantly greater percent vegetative matter (63% ± SE 12%) than anthropogenic diets (8% ± SE 3%) [H = 8.44, d.f. = 1, p < 0.01]. Novel organic and inorganic items found in anthropogenic diets included bacon, glass, hot dog, pellet meal, and plastic. This study suggests that anthropogenic resources may have the ability to support this species’ establishment. Further investigation, of ecologically similar species, may elucidate linkages between resources in urbanized areas and impacts in nearby natural habitats.
