Complex sentence: Their calls consist primarily of a grating alarm call and a descending piping call, the latter of which is diagnostic for the bird being significantly different in timbre and melody to that of other birds sharing their habitat.
Split into simpler sentences: Their calls consist primarily of a grating alarm call and a descending piping call. The latter call is diagnostic for the bird in the wild, being significantly different in timbre and melody to that of other birds sharing their habitat.