This project will focus on variation in timing of breeding decisions in a seasonally breeding bird. Previous research has shown that earlier breeding individuals have higher reproductive success and optimize timing with peak food abundance, but the underlying physiological mechanisms of individual variation require further exploration. Egg production has a high energetic cost to females, requiring allocation of resources away from individual maintenance and into current reproductive success. Individuals that are not in good enough condition to take on the energetic trade-off of reproduction are predicted to have a later egg lay date. Manipulations will attempt to mimic a negative energy balance, thus delaying reproduction as a proxy of low food abundance, disease, or poor condition. The