Josh Hayes nailed it! They are mocking any notion of getting some sleep!
While conducting bird surveys in New Mexico years ago, I was kept awake one
night by a persistent mocker who belted out his non-stop improvisations
from atop a juniper tree adjacent to my camp site.

There is a singular beauty in a Mockingbird singing under the light of a
full moon during a cool high desert night. But morning and the coming work
weren't going to wait for me to get adequate sleep. I finally got out of my
sleeping bag, jumped out of the truck bed, and flung a handful of pebbles
in the Mockingbird's direction. He took the hint and retired to a safer
distance, resuming his relentless soliloquy, but now not so deafening. So
we compromised, and I finally drifted off under the mocking moonlight.

Of course in the southwest they mimic the local birds: Cassin's Kingbirds,
Say's Phoebes, Curve-billed/Bendire's Thrashers, Ladder-backed Woodpeckers,
Scaled Quail, Scott's Orioles, etc. And confusingly, because its song
structure is not unlike the Mockingbird's, Rock Wrens.

Mike,
in Bellingham
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