Variation in the songs of three species of Estrildine Grassfinches

Abstract

One hundred and ninety-sir song phrases mada by forty-two individuais were ana!ysed sonagraphically. The birds belonged to the forms Poephila p. personata and leucotis, P. c. cincta and atropygialis, P. a. acuticauda and hecki. The songs of grassfinches are very soft and audible only at close range. They do not have an advertising function but are used during courtship just before copulation; there is also an Undirected Song. All three species show variation in structure of the song of the same type and some to the same degree as that of most passerines. There is variation between species, subspecies, geographical populations and individuals. The advantage of having variation in close contact signals such as grassfinch songs remains unknown. There are evolutionary trends in Poephila to modify the structure of the song by ,increasing its structural segmentation, the stereotypy and duration of its phrases and elements, its loudness and musicallty. These features have their weakest expression in P. bichenovii and P. guttata and their highest in P. acuticauda.