According to the Audubon Society’s Field Guide to North American Birds, “The Bobolink was probably confined to the central grasslands originally, but with the settling of the Northeast it quickly spread into New England. Now with farms abandoned and the land returning to forest, the species is declining.”
In Harpswell, a large portion of Mitchell Field is left undisturbed to allow the nesting of birds such as the Bobolink. The video and audio is from that site in June of 2013.