Food availability and immune capacity in serin (Serinus serinus) nestlings

Parental feeding effort is an important determinant of chick development in birds. Quality and amount of food provided to each nestling, however, migh t affect the development of the immune system. Food availability around the nest site may account for part of the difference in body condition and imm une capacity of nestlings. We tested this idea in the socially monogamous s erin (Serinus serinus), investigating growth and immune capacity of nestlin gs in relation to food availability around the nest site. We used a set of immunological and serological assays, including antibody responses to sheep red blood cells (SRBCs), the T lymphocyte cell-mediated immune response (P HA), granulocyte:lymphocyte ratio (G:L), haematocrit and sedimentation rate . The results suggest that serins raised under poor environmental condition s were less immunocompetent. The immune response to PHA and SRBCs significa ntly increased with food availability. Haematocrit values were positively, sedimentation rate and the G:L ratio negatively correlated with food availa bility. Similar results were obtained when examining chick development in r elation to the immunological and serological variables. However, there was a negative relationship between parental feeding rates and food availabilit y, as well as between parental feeding rates and chick development. We conc lude that body condition and immune capacity of nestlings are strongly corr elated with the availability of food around the nest site.