Complex sentence: This, termed "Type II Vocalization", is song-like and used when confronted by calling butcherbirds and sometimes other predatory birds, but its purpose is unknown; it is certainly not a warning call.
Split into simpler sentences: This, termed "Type II Vocalization", is song-like and used when confronted by calling butcherbirds, and sometimes other predatory birds. Its purpose is, however, unknown; it is certainly not a warning call.