Immunological development in nestling American kestrels Falco sparverius: post-hatching ontogeny of the antibody response

Avian research involving examination of immune function or testing of immunocompetence in wild birds has been based upon information on Galliforms, (chicken and quail) even though they are precocial, whereas most wild species with which ecologists, biologists and toxicologists work are altricial; blind, naked and completely dependent at hatching. Here we begin to address this gap in knowledge, offering insight into the early, post-hatching, humoral immune response in an altricial bird, the American kestrel (Falco sparverius). Over two breeding seasons, nestling kestrels were immunized with a non-pathogenic antigen, dinitrophenol keyhole limpet hemocyanin (DNP-KLH), between 3 and 9 days post-hatching and boostered 6 days later. Background levels, primary and secondary immune responses were measured using an enzyme linked immunosorbent assay. The specificity of our laboratory produced rabbit, anti-kestrel antibody was determined using a double immunodiffusion assay. Results showed the rabbit antiserum to have specific anti-kestrel IgG activity. Birds as young as three days old could successfully mount an antibody response, the magnitude of which increased with age at first vaccination. Early immunization did not compromise growth rate, nor did it affect the maximum secondary response. Comparatively, adult kestrels immunized during the same season and following the same protocol, had antibody levels four times higher than those of the nestlings.