Ruby-crowned kinglet was a significant “player” in the book Winter World: The ingenuity of animal survival by Bernd Heinrich; you may know that he teaches a course Winter Ecology. John Burroughs writes about this bird “How does the Ruby-crowned Kinglet know that he has a brilliant bit of color on his crown which he can uncover at will, and that has great charm for the female? … My ear was attracted by the fine, shrill lisping and piping of a a small band of these birds in an apple-tree…There were four or five of them, all more or less excited, and two of them especially so. I think the excitement of the others was only a reflection of these two. …the two birds were entirely occupied with each other. They behaved exactly as if they were comparing crowns, and each extolling his own.” Burroughs is always interesting in how he presents his observations of the natural world.