Listen for Birds

I spent the majority of my childhood weekends outside. I learned young to listen for the birds comings or goings for the signal of spring or fall. Without fail the weather would change within three days of hearing a goose's call.

One morning [in the cold of winter] I awoke of the sound of chirping of birds outside my bedroom window.  It sounded like a pair of birds were arguing, the fact that I thought that made me think. [Why did think they were arguing?] One bird would start a long blast of chirps, when another bird [with a lower song] would cut in over top of the first, and tweet the same number of chirps.

I was impressed that I could tell that one bird was lower then the other, but even through I heard this exchange repeated maybe six times I couldn't how many chirps each were doing.