Diet and ectoparasites of ring-billed gull chicks in a marine environment on Prince Edward Island.

摘要

This thesis has two distinct foci. First, I investigated the diet of Ring-billed Gull chicks in a marine environment, on Prince Edward Island (PEI), using soft regurgitant collection and stable isotope (delta13C and delta15N) analysis of both regurgitants and blood samples. I compared isotopic signatures of blood of Ring-billed Gull chicks to blood of chicks from sympatrically nesting Herring and Great Black-backed Gulls. Ring-billed Gulls use marine food sources to feed their young when nesting in a marine environment. Furthermore, Great Black-backed Gulls feed their young more marine food than both Herring and Ring-billed Gulls.;In the second part of this thesis, I investigated relationships among stress, immunocompetence, and ectoparasite loads of Ring-billed Gull chicks. Ring-billed Gull chicks from PEI host three species of lice: Quadraceps punctatus, Saemundsonnia lari, and Austromenopon transversum . Immunocompetence was assessed with a phytohaemagglutinin skin assay (PHA) and with differential leukocyte counts, while stress was assessed using the heterophil to lymphocyte ratio (H/L). Significant relationships were not observed among PHA, H/L, and louse loads. However, greater total louse loads and numbers of A. transversum were associated with higher proportions of leukocytes that were eosinophils. Eosinophils are involved with the innate immune response, the first line of defence against parasites. Furthermore, larger chicks had more lice. Overall, louse load was not linked with stress or PHA response but was associated with the innate immune system of Ring-billed Gull chicks, as measured by eosinophils. (Abstract shortened by UMI.).