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Abstract

Parasites can influence important ecosystem characteristics, such as biomass, biodiversity, food webs, and species interactions. Parasites of birds, in particular, offer a unique opportunity to test questions about parasites with complex life cycles (those that require more than one host for completion) and how host life history traits affect parasitic infections. For example, there is evidence that migratory versus non-migratory behavior in birds can affect the parasites present in a host, although whether migratory birds have more or fewer parasites is unclear. To help address these knowledge gaps, we collaborated with airports, animal rescue/rehabilitation centers, and hunter check stations in the Bay Area of California to collect 57 raptors, waterfowl and herons for parasitological analysis. We performed detailed dissections of the gastro-intestinal tract and identified 64 taxa of parasites: 5 acanthocephala (thorny headed worms), 24 nematoda (roundworms), 8 cestoda (tapeworms), and 27 trematoda (flatworms). We then used generalized linear mixed modeling to determine how life history traits influenced parasite richness (number of taxa present) among bird hosts. We found associations with clutch size, diet and migratory status: parasite richness was greater in birds that were migratory, had literature and has been linked to immune system function and parasite exposure respectively, whereas the effect of migration supports one of the two opposing hypotheses which are a topic of ongoing debate. These results add to the growing knowledge of how host life history can influence parasitic infections, especially with respect to the role of migration on parasite richness.