Fig. 6. Energy budgets and flight times in different environments. Also shown (far right) is the hypothetical budget and flight time in the poor environment of starlings that maintain high body mass the same as in the rich environment. E_flight is the energy spent on flying, BMR_night is the energy spent during the night on BMR only, E_night is the total energy spent during the night, and E_{nonfly day} is what is spent during day-time when not flying. The broken lines in the hypothetical energy budget indicate the surplus energy that would have been spent due to the extra time spent flying (and less time spent not flying), and the extra energy that is spent on flying due to the body mass increase. The total daily energy expenditure (DEE) budget is shown on top of each bar.