Part 1: Organisation. Starlings have two categories of song: whistled and warbling song. We describe first the structure and organisation of the warbling song of individual birds from widely separated geographic origins. In all of these the warbling category is seen to be an extremely complex performance which includes strongly contrasting note types and even simultaneous production of very different notes. In the next level of organisation the notes are grouped into units, the motifs, each of which is sung from 1 to 12 times before the bird goes on to the next. Finally these motif groups are arranged in a definite sequence, although not every motif is present in each song. Songs are long, ranging from 30 to 50 seconds in duration. Warbling is an essentially individual performance in that, except for 2 or 3 species-specific motif types, the others are all characteristic of an individual bird. The beginnings and endings of the songs are clearly defined, the sequences opening usually with an individual motif type and closing with a species-specific one. There are large differences between individuals in the size of the repertoire which may extend from about 20 to more than 35 motif types. Part 2: Year to year changes. Further to these general studies, birds in a starling colony have been observed over a period of two years to determine whether the song structure of a given individual changes with time. The age and reproductive status were taken into account. The changes observed differed according to whether they were songs characteristic of an individual bird that were considered or whether they were of the species-specific type. No modifications in the structure of the species-specific whistles were observed from one year to the next, whereas each bird totally renewed its repertoire of individual whistle types. The changes in the warbling song depended on the age of the bird: a very young individual totally renewed its repertoire from one year to the next, whereas others added only new motif types to their repertoire. These results show that even o1d individuals can acquire new song elements.