Timing of migration into the tropics was correlated with an individual's post-breeding energetic condition in August as measured by (a) plasma β-hydroxybutyrate, (b) triglyceride and (c) growth bar width of the rectrix. Open symbols are 1-year-old breeders, closed symbols are 2 years or older. (a) rs, −0.78; p, 0.008. (b) rs, −0.64; p, 0.05. (c) rs, −0.62; p, 0.02.