Several authors have reported associations between birds and monkeys in tropical forests (Boinski & Scott 1988, Huettmann 1999, Ruggiero & Eves 1998, Terborgh 1990). By such associations birds are considered to get some benefit, such as protection from predators and/or greater feeding efficiency (Terborgh 1990). In Southeast Asia, however, few reports on such interspecific associations have been available (galetti & McConkey 1998). The exception concerns several species of macaques living on Sulawesi Island, Indonesia (Fooden 1969). Associations between birds and Sulawesi macaques have been descibed by researchers as well as bird-watchers (Coates et al. 1997, Jepson & Ounsted 1997, Martarinza et al. 1994, Whitten et al. 1988). Local people in Sulawesi also know of associations between macaques and certain birds, particularly hair-crested drongo (Dicrurus hottentotus) and yellow-billed malkoha (Phaenicophaeus calyrhynchus). The farmers call these birds ‘burung monyet’ (monkey birds) and use the conspicuous calls of drongos and malkohas as signs of macaques' approaches to their fields (S. Matsumara, pers. obs.).