A music professor I had in grad school once remarked that chickadees know music theory because their songs sound like ‘re-do’ and therefore imply an authentic cadence.
For those not familiar with Western tonal music theory, the point was that the song of the Chickadee has a sense of completion and resolution, as opposed to being incomplete and unresolved. Those two pitches back-to-back (re-do, or supertonic and tonic, or if you’ve got an instrument near you, any note followed by a note exactly one whole step lower) is, perhaps, one of the most fundamental melodic sequences in Western tonal music.