… When I started hiking desert canyons a few years ago, I kept hearing the song of a bird I couldn’t see, a long descending series of sharply whistled notes. It was a canyon wren, I learned from the books, but what I learned form the bird was more important. It sang as I woke up, as brilliant sun spread down the great red walls, and it sang as I started farther up the twisting canyon, sloshing through pools and scrambling up dry water chutes, higher and deeper into the carving of time. And what I remember most vividly from those early hikes is no particular thing I saw, no one fern grotto or sandstone spire, no cottonwood or cactus garden. I remember a bird I couldn’t see that called from around the next bend, from over the brink of a dry waterfall where the upper walls held the blaze of sky, where even as it steadily opened itself to sight, the canyon receded further and further into the depth of its mystery.