SONG FREQUENCY PLASTICITY AND COMPOSITION OF PHRASE VERSIONS IN GREATTITS PARUS-MAJOR

In Great Tit song, a phrase of one to five notes is rapidly repeated i n a strophe of a few seconds long. Great Tits sing up to 100 strophes of a single phrase Version in a bout before a new phrase version is in troduced. In 49 out of 69 phrase versions from 34 Great Tits analysed, phrases were repeated in a stereotyped fashion within strophes and wi thin bouts. In the other 20 phrase versions, between 2 and 61% of the strophes showed song frequency plasticity (SFP). SFP is a phenomenon i n which consecutive ph rases within strophes are not 'identical' in st ructure because of abrupt differences in frequency characteristics acr oss phrases. The percentage of strophes with SFP was significantly hig her in phrase versions with (1) a higher note rate within strophes, (2 ) higher note frequencies (kHz), and (3) shorter notes. I suggest that motor constraints determine SFP and that these constraints play an im portant role in the manner in which Great Tit phrase versions are perf ormed and composed.