why the raven

Years ago, when the wall was first built, an older cottonwood had been telling a neighbor about the changes in their local human population. 

The humans [the cottonwood said in the early spring]
are becoming [summer]
more anxious [autumn].

The neighbor replied: 
What is [spring]
exciting them [summer]?

The cottonwood paused, and tasted the air.
Each other [spring].

---------

The stones in the mountain began a new song. The first note sounded like a distant drumroll, and it lasted three years.

The second note the stones sang began like a crack of lightning and sounded like the pouring rain.