ABSTRACT
Despite the traditional quips about “bird brains”, most birds actually possess rather large and complex brains (Pearson, 1972; Striedter, 1997; Nieuwenhuys et al., 1998). This is not particularly surprising, for birds also exhibit remarkably complex behaviors, many of which can be modified through learning (MacPhail, 1982). It has long been known, for example, that songbirds (Fig. 1) can sing and imitate complex songs (Thorpe, 1961). During the last 30 years much has been learned about the behavioral details of song learning and its neural mechanisms (Nottebohm et al., 1976; Nottebohm, 1980; Konishi, 1985; Brenowitz et al., 1997). This research has shown that the brains of songbirds change in numerous anatomical and physiological attributes during the time that birds typically learn their songs. The principal aim in the present paper is to review these correlations between neural and behavioral change and to assess the extent to which they represent causal relations. Beyond the scope of the present paper are the details of birdsong perception, production, sexual differentiation, and evolution (see Arnold, 1997; Bottjer, 1997; Brenowitz, 1997; Goller and Larsen, 1997; Hamilton et al., 1997; Margoliash, 1997; Marler, 1997; Nottebohm et al., 1990; Nowicki and Marler, 1988; Schlinger, 1997; Suthers, 1997; Vu et al., 1994; Wild, 1997).
