Résumé
The size of the song repretoire of great tits, Parus major, was examined in realtion to the variation within a repertoire of three song measures (proportion of sound in a phrase, frequency and phrase duration) and to the composition of a repertoire (the song types that constitute a repertoire). Larger song repertoires were more variable. Song types with either a high proportion of sound or a high frequency were more frequently used by males with large repertoires (five to seven song types) than by males with small repertoires (two to four song types). Song types with either a low proportion of sound or a low frequency were used by all individuals in the study population. A comparison of field data and random simulations suggested that factors other than random learning of song types could affect the composition of a bird's repertoire. It is proposed that, besides learning opportunities and learning ability, constraints in singing ability influence the composition and/or size of great tit son repertoires.