When caring for offspring of equal value, parents may benefit from equal allocation of limited resources. However, if some offspring are more promising than others, parents may instead benefit from diverting resources to high-value individuals. In birds, nestlings display brightly colored mouth parts that may allow parents to assess the relative quality of chicks. In nestling house sparrows, for example, the intensity of yellow mouth coloration is positively associated with condition, and parents deliver more food to more yellow nestlings. This project further examines the relationship between coloration and nestling health. First, a study in which partial broods are cross-fostered will examine the relative contribution that pre- and post-hatching environment make to mouth color. If rearing environment explains most variation, this will suggest that color integrates information about post-hatching conditions (e.g. diet, parasite infection). If parentage explains most color variation, this will suggest that colors may instead reveal nestling qualities driven by genetics or characteristics of the egg (maternal effects). A second experiment examines the effects of a blood-sucking insect parasite, and a virus that it transmits, on nestling mouth color. If mouth colors are associated with nestling health, nestlings exposed to parasites and virus should be less yellow than nestlings not exposed, and color should positively predict the ability of nestlings to withstand infection. Together, these two studies examine how nestling mouth color integrates information about past challenges and predicts future resilience, as well as identifying possible genetic and pre-hatching constraints on this signaling system. This project will offer insights into why parents benefit from favoring certain offspring as well as identify correlates of infection survival in wild birds. Broader impacts of this project include training of a graduate student, mentorship of an undergraduate student and contributions to exhibits at the Oklahoma Museum of Natural History and to the Oklahoma City Zoo.
