1. Inactivating one L1 results in angular errors and circling during orientation toward the side having the intact L1 in response to calling songs (CSs) whose intensities are below the threshold for L3 (Figs. 2, 3A). When song intensities are increased above the threshold of L3, circling decreases (Fig. 3B). 2. Following inactivation of one L1 and occlusion of the ear providing input to the intact L1, no phonotaxis occurs in response to CSs at 60 dB (below the threshold of L3; Fig. 4A) demonstrating the necessity of L1 for phonotaxis. Orientation, at large and consistent angular errors (Fig. 5A) and circling (Fig. 5B) to the unoccluded side resumes when song intensities are increased above the threshold of L3 (Fig. 4B) suggesting that a single L3 can induce phonotactic responses. 3. Inactivation of one L3 causes angular errors in orientation when CSs are above its threshold (Figs. 6A, 7), which are not apparent when CSs are below L3's threshold (Figs. 6B, 7). 4. Inactivation of one L3 and occlusion of the ear providing input to the contralateral L1 and L3, leave only one L1 functioning. This results in turning and circling toward the unoccluded side containing the one functioning L1 (Figs. 6C, 8), thus confirming the sufficiency of L1 for phono taxis. © 1992 Springer-Verlag.