There are so many improvements on bird technology…I come from a time (recently) where field guides ruled…now there is this.This can be brought at the Cornell Field Lab for Ornithology.
Warblers and spectrograms of their nocturnal flight calls. Black-throated Gray Warbler by Roy Brown; others by Laura Erickson.
See the Rosetta Stone for Warblers
By day, warblers dazzle us with their colors and songs. By night, they migrate unseen, uttering calls lasting a fraction of a second. Using the “Rosetta Stone for Warblers,” the Cornell Lab is creating tools to listen to the night sky and identify the birds passing overhead. Thanks to new grants and gifts, we’re also developing a project called BirdCast to forecast migration using radar, sound, weather data, and observations from eBird. See the Rosetta Stone for Warblers.