He had a challenger: another male kinglet intruding upon his fiefdom, and that individual was hiding in, or around, of all places, my wife’s pickup truck that was parked alongside the driveway. 

The Ruby-crowned Kinglet would descend from the adjacent trees and, with relentless tenacity, make rounds of the various reflective surfaces of the truck, with particular attention focused upon the front bumper. Then, most likely exhausted after several minutes of extreme exertion, he would disappear into the surrounding foliage, only to remount his siege of the truck five or ten minutes later. His dazzling display of dominion was exhausting to watch, and I was just sitting on the ground. My prince valiant hopped onto every reflective surface of the truck …. onto the front bumper, then the rear bumper, onto the windshield, then the side mirrors, even the passenger side window, fluttering its wings feverishly, pecking and scratching at his rival. Again and again. Photos and video