Male canaries, Serinus canaria, sing a special phrase ('A') that elicits very high levels of sexual display in conspecific females. This phrase is characterized by the repetition of a complex but brief two-note syllable. We tested the sexual responsiveness of female canaries to these A phrases, extracted from eight male repertoires. Five of the phrases elicited very high levels of copulation solicitation displays in the females. We suggest that the females may use the very rapid temporal patterning of the distinct notes in these two-note syllables to assess male quality. These syllables may be an honest indicator of a male's condition and may thus attract and arouse females. Copyright 1998 The Association for the Study of Animal Behaviour.