Feeding ecology and epizootological value of the Great Cormorant (Phalacrocorax carbo) during the secondary expansion of the Baikal region

Aim. To research the Great Cormorant (Phalacrocorax carbo L., 1758) ecology during the secondary expansion of the Baikal region. Material and Methods. The material for studying cormorant nutrition was 28 stomachs of harvested birds, visual observations of feeding cormorants using optical equipment, as well as regurgitated burps of nutrition obtained by a bloodless method when being fed to chicks. 21 examples of cormorants were the subjects of the parasitological research. Results. The number of the species has been growing since the beginning of the XXI century and, starting from 2020/21, is likely to stabilize, remaining at a high level. This indicates the gradual integration of the species into the Baikal Lake ecosystem. The main food item of Cormorants are the non-commercial fish, Sleeper (Percottus glehni Dyb.), Perch (Perca floviatilis L.) and Roach (Rutilus rutilus L.). Parasitological studies have revealed 8 species of helminths from three classes with varying degrees of invasion. Only one of them, Contracaecum osculatum baicalensis (Mosgovoy et Ryjikov, 1950), is endemic and potentially dangerous to human health (its infection rate can reach 80%). Conclusion. The Great Cormorant is an obligate, but not a specialized ichthyophage, focused on the prevailing fish species. Great Cormorants as hosts of ticks, helminths and other ecto- and endoparasites are potentially sources of threat to the occurrence and spread, primarily, of ornithoses and helminthiasis in the Baikal region and possibly of other diseases carried from their wintering places.