The parameters of species richness, abundance and diversity of the intestinal helminth infracommunities of a sample of 269 Common gulls, Larus canus, were examined over one season at Agdenes, Norway. The communities developed rapidly in unfledged gulls and the diversity parameters were of similar magnitude in immature and adult birds. All parameters were low in the early part of the season, reached maxima in June or July and fluctuated erratically or declined thereafter. Comparison of summary parameters with those from other species of gulls indicated that helminth community diversity in Common gulls is fairly typical of gulls in general. In gulls as a group, helminth communities show common features of high species richness, low abundance, few or no core species and a number of species that occur rarely and in low numbers. Expectations of particularly high parasite community diversity were not fully realised because species lists and diversity of the component community are not a very good basis for predicting diversity at the infracommunity level.
