The distance call is emitted when a bird is visually separated from other birds (Zann, 1996). Distance calls are special in Bengalese finches and zebra finches in that the calls are sexually dimporphic (Guettinger and Nicolai, 1973). In Bengalese finches, male calls are narrow banded, pure tonelike vocalization with rising frequency modulation while female calls are wide-banded, pulse trainlike utterances (Okanoya and Kimura, 1993; Yoneda and Okanoya, 1991).