In the Sound Issue of Ecotone Magazine, The Voices of Birds describes the communication styles of the evening grosbeak.
I used a reference map supplied by Kendra Sewall, the author of “The Voices of Birds”, as a starting point. The main issue with the source map is that it wasn’t high enough resolution for print media, and that it didn’t incorporate the spectrograms of the various geographic regions.
The final version of the map below spread a full spread (note that a seam would run through the middle).
The original source of data for all of these maps is BirdLife International.