Characterization of four toxins from Buthus martensi scorpion venom, which act on apamin-sensitive Ca2+-activated K+ channels

What are the relative roles of imitation, improvisation and invention in the development of large song repertoires in species of the songbird family Mimidae? This question was addressed in a laboratory study of the vocal development of young grey catbirds, Dumetella carolinensiscollected from western Massachusetts. Two groups heard a repeated 10-s, tape-tutored segment of catbird song, two other groups heard a repeated 16-min segment and a fifth group heard no tape-tutored songs. One male selected for study from each group developed a large repertoire of seemingly normal songs, and wild males responded strongly to songs of the male that had heard no tape-tutored song. Relying little on precise imitation and largely on improvising or inventing, each male developed a highly unique repertoire. A geographical survey of catbird song revealed little to no evidence of song sharing or microgeographical variation, which is consistent with the idea that imitation plays a relatively minor role in song development. Perhaps simultaneous selection for large repertoires and reduced geographical variation has led to such an emphasis on song individuality and non-imitative developmental processes.