the finding that drove their hypothesis was that the males were able to recover a high percentage performance by switching song types. if the male was producing shorter strophes and having longer inter-strophe pauses (low percentage performance), then by switching to a different song type the bird would once again be able to produce longer strophes and have shorter inter-strophe pauses. lambrechts and dhondt proposed the anti-exhaustion hypothesis, which provided both a functional and casual explanation for the song switching behaviour in birds along with having song repertoires.