24 June 2010. This year I have banded a male in Northfield (above) and observed a singing male at the Carleton Arboretum (below). Listen to the song (used with permission of Thayer Birding Software).
Hatchling Indigo Buntings learn their songs from nearby males--not, as you might assume, from their fathers. In fact, buntings raised in laboratories, only hearing their fathers' songs, grow up to sing strange songs unrecognized by wild buntings. Thus, in the wild, "song neighborhoods" are formed, with song themes that persist for up to ten generations. These song types are fluid, and are affected by the songs of foreign buntings new to the neighborhood (Payne 2006).
Payne manipulated recorded Indigo Bunting songs (by slicing tapes in the days before computers). Buntings recognize their species by note pitch, spacing, and length. They recognize individuals by details of note structure. Indigo Buntings are more aggressive towards strangers. Birds also communicate their intentions by song length and singing rate (Lehner 1996).