the results from the study showed that singing performance improves with time throughout the morning. this was explained only by the warm-up hypothesis, the cumulative number of songs that the bird had sung that morning. the other hypotheses were found to have no effect on singing performance, including the song type specific hypothesis which is consistent with the anti-exhaustion hypothesis. schraft et al. proposed that the anti-exhaustion hypothesis and the warm-up hypothesis are not mutually exclusive as the birds that warm up still may need to switch song types because of fatigue.