Is identification of warbler migration night calls possible? How do we ID warblers from their night migration calls?

Yes, based on the amazing recent work of researchers at Cornell Lab’s Conservation Science program.

They've developed the so-called "Rosetta Stone" or magic potion that utilizes spectrograms to identify nocturnal (night) migrrants.

These spectrograms (adjacent graphic) are a visual representation of the very brief flight calls made by North American warblers during their nocturnal migrations. Some of these call notes sound almost identical to our ears, but spectrograms show minute differences between them. Scientists can compare spectrograms of night recordings to spectrograms of known species to identify nocturnal migrants in total darkness.

(* = Andrew Farnsworth, a scientist in the Cornell Lab’s Conservation Science program, developed this “Rosetta Stone” in 2006 in collaboration with Michael Lanzone, Cellular Tracking Technologies, William R. Evans, and Michael O'Brien.)

The spectrograms correspond to all 48 warbler species of the U.S. and Canada (including Grace’s and Red-faced warblers, not shown), and is a major tool in the Lab's Acoustic Monitoring Project.