The role of incubation behavior in shaping developmental physiology in a wild Passerine

The environmental conditions under which an organism develops can impact both short and long-term phenotypic expression. In birds, developing embryos may be particularly sensitive to changes in incubation temperatures, particularly those outside the range of optimal embryonic development. Variation in incubation temperatures may therefore have important effects on the development of key phenotypes, including critical physiological systems such as innate immune defenses. Effects of incubation temperature on embryonic development are well documented in domestic birds, but comparatively little is known regarding such effects in wild bird populations. We experimentally manipulated the incubation temperature of American Robin (Turdus migratorius) eggs to better understand how thermal variation during this critical period can affect innate immune defenses in a wild passerine. A single egg per active nest was collected at clutch completion and randomly placed in one of two temperature treatments, 36°C (suboptimal) and 38°C (optimal). Hatched nestlings were returned to a foster nest of the same age. Blood samples were taken from each artificially incubated nestling and a natal sibling (to control for genetic or parenting effects). Collected blood samples were then used to assess bacterial killing ability (BKA). In 2015 we found that optimally incubated individuals had the highest BKA, natural individual had second highest, and suboptimal individuals had the lowest BKA. Based on preliminary results, it appears that incubation temperatures do play a discernable role in developing individual immunocompetence. Therefore, factors influencing incubation patterns of female birds may have lasting effects on development of juvenile birds.