The costs of immunological challenge to developing mountain chickadees, <i>Poecile gambeli,</i> in the wild

Abstract

The tradeoff between immunocompetence and development in avian species could have long‐term consequences relating to fitness. This study investigated the developmental cost of mounting a humoral immune response in growing mountain chickadees, Poecile gambeli . We immunologically challenged nestling chickadees using nonpathogenic antigens of either Newcastle disease virus vaccine or sheep red blood cells. Body mass, tarsal length, haematocrit, total plasma protein, and survival did not vary significantly between antigen treatment groups and control groups. Developmental stability was assessed using fluctuating asymmetry (FA) between the right and left ninth primary feather length. FA was increased significantly in the antigen‐challenged birds. This result indicates that the up‐regulation of the humoral immune response was developmentally costly to the nestlings by causing an increase in FA.