Call-note discriminations in black-capped chickadees (Poecile atricapillus).

Bioacousticians (M.S. Ficken, S. R. Ficken, & S. R. Witken, 1978) classified black-capped chickadee call notes from the chick-a-dee call complex into 4 note types (A, B, C, and D) identified from sound spectrograms. In Experiment 1, chickadees (Poecile atricapillus) learned operant auditory discriminations both within and between the 4 note types but learned the between note-type discrimination significantly faster. In Experiment 2, when the original, unrewarded between-category exemplars were replaced with novel, rewarded exemplars of these same categories, chickadees showed transfer of inhibitory stimulus control to the novel exemplars. In Experiment 3, when novel exemplars were replaced by the original exemplars, chickadees showed propagation of positive stimulus control back to the original exemplars. This evidence suggests that chickadees and bioacousticians accurately sort conspecific call notes into the same open-ended categories (R. J. Herrnstein, 1990).