Comparison of the helminth fauna of eastern and western kingbirds at Delta Marsh, Manitoba

Forty-six Tyrannus tyrannus (L.) and 35 Tyrannus verticalis Say from Delta Marsh, Manitoba, were examined for helminths during the summer of 1977. Eighty-three percent of T. tyrannus and 94% of T. verticalis were infected with at least one species of helminth. Nine helminth species (four trematodes, one cestode, three nematodes, and one acanthocephalan) were found, eight from T. tyrannus and seven from T. verticalis. Six species were common to both hosts. Six new host records are reported for Tyrannus tyrannus and seven for T. verticalis. Tyrannus verticalis had a significantly greater total helminth burden than T. tyrannus did. Plagiorchis noblei was the most abundant parasite in each species, accounting for 69% of the helminths of T. tyrannus and 96% of those for T. verticalis (this difference is significant). Plagiorchis noblei was the only helminth found in juvenile hosts.This study further supports the following hypotheses: (1) that P. noblei is a northern parasite transmitted only in breeding habitats of its hosts; (2) that juvenile birds show greater intensities of infection than adults; and (3) that the number of parasite species is greater in adult birds than in juveniles.