Incubation temperature affects the metabolic cost of thermoregulation in a young precocial bird

1. The developmental environment plays a key role in determining offspring phenotype, and the parents behaviour and physiology often dictates developmental conditions. Despite the plethora of studies documenting the importance of incubation temperature on offspring phenotype in reptiles, very few studies have examined such relationships in birds. 2. Because nearly all birds physically incubate their eggs, altering the nest environment may be an important but previously overlooked way parents can influence their offspring's phenotype. Here, we tested the hypothesis that incubation temperature would affect thermoregulation in wood duck (Aix sponsa) hatchlings. 3. We show that a reduction in < 1 degrees C in incubation temperature affects the metabolic costs of thermoregulation in offspring of a non-domesticated bird, resulting in 27-40% greater increases in oxygen consumption of ducklings incubated at the lowest temperature relative to ducklings incubated at higher temperatures. 4. Because we demonstrate that incubation temperature affects hatchling phenotypic quality, our findings provide novel support for newly proposed frameworks that highlight the importance of incubation temperature to the evolution of clutch size in birds.