Multi-year dietary and parasitological investigations of invasive Egyptian geese (Alopochen aegyptiaca) in central Germany.

The Egyptian goose Alopochen aegyptiaca, native to Africa, was introduced to Europe between the 17th and 20th centuries as an ornamental and park bird. Since then, it has spread widely and has reached very high population densities in several countries, including Germany. In 2017, it was listed as an invasive alien species of Union concern, because its continued spread may have ecological impacts. To investigate its feeding ecology and parasite fauna, 100 Egyptian geese from the Wetterau region in Hesse, Germany, were examined over four years. Their diet consisted mainly of plant material, particularly corn, grasses and grains, but also included animal components such as mussel fragments and annelids. Parasitological analyses identified six ectoparasite and eleven endoparasite species. Anaticola asymmetricus, Anatoecus dentatus, Echinostoma revolutum, Notocotylus attenuatus and Polymorphus minutus occurred in all study years and were classified as key species. The dietary results indicate opportunistic use of abundant and easily accessible resources, with temporary preferences for certain resources in the study area. The parasite fauna was highly diverse and substantially expands the known parasite spectrum of the Egyptian goose, including seven first records for Europe. Combining dietary and parasitological analyses demonstrated that animal components constitute a certain proportion of the diet and enables inferences about earlier feeding events. Food availability and parasite occurrence are likely influenced by ecosystem conditions, the presence of potential intermediate and definitive hosts and climatic conditions. Overall, this study provides a comprehensive overview of the feeding ecology and parasite fauna of Egyptian geese in the study area and broadens current knowledge of their parasites in Germany and Europe.