Two Song Types of Black-throated Blue Warbler

I've known about the "Cerulean" type song type for many years, as birds breeding in central MA and southern NH sing it, and sometimes confuse birdwatchers because of the similarity to Cerulean warbler songs. For some reason I thought that the migrants in eastern MA did not sing it. This was obviously wrong, as I started to recognize it at Mt. Auburn several years ago. I didn't have any video of this song when I was finishing "Listening to Warblers" (Listening to Warblers) last year, so I left it out.

I know that individual birds can sing both song types. This day at Mt. Auburn there were several singing males in the tall oaks and maples on the NW side of the cemetery.

If this is a regular song at Mt. Auburn, it suggests populations to the northeast sing it, perhaps as far as Canada. So, I really don't know what the range of this song might be!

This species sings other odd songs on its breeding territory.