Figure 3.

Swamp sparrow note categories and syllables. (a) Marler & Pickert [50] originally defined six categories; sub-categories Ia and Ib were split by Lachlan et al. [74] based on cluster analyses of acoustic characteristics. Syllables are assembled from 2 to 5 note categories, and songs are formed by repeating a single syllable (individual birds sing 2–5 different songs [74]). (b) Individual notes can be characterized largely by their duration and change in frequency. When notes are clustered using this approach using Gaussian mixture models, populations in New York and Pennsylvania differ in number of clusters and where those clusters are located in acoustic space. After Lachlan et al. [73,74].