Figure 1.

Examples of syllable types in three species with increasing levels of syllable diversity. (a) Song of the Bewick's wren (Thryomanes bewickii) with a single syllable type repeated. (b) MacGillivray's warbler (Oporornis tolmiei) with three syllable types. (c) Lincoln's sparrow (Melospiza lincolnii) with eight syllable types. Syllables may be composed of a single note as in syllable ‘e’ of the Lincoln's sparrow song or of multiple repeated clusters of notes as in Bewick's wren. Fast trills as in syllable ‘c’ and ‘h’ of the Lincoln's sparrow song are each considered a single syllable.