Neuropeptide Y and orexin immunoreactivity in the sparrow brain coincide with seasonal changes in energy balance and steroids

The transition between the breeding and nonbreeding states is often marked by a shift in energy balance. Despite this well‐known shift in energy balance, little work has explored seasonal differences in the orexigenic neuropeptides that regulate food intake in wild animals. Here we tested the hypothesis that free‐living male song sparrows ( Melospiza melodia ) show seasonal changes in energetic state, circulating steroids, and both neuropeptide...