Raven song

The raven is considered the largest songbird in North America. I sometimes wonder how much information is actually contained in the wide variety of noises they make -- to what extent they're actually talking to each other. Today I was walking Lucky in our 6" of new-fallen snow and a raven came flying down the valley from the north, making a distinctive call that I have not heard from a raven before -- a series of four bell-like tones, three short and one long with a lilting uplift at the end. It stopped every 50 yards or so to sit on a treetop or telephone pole, making its distinctive call, and then flew on. It swooped over us, about 10 feet above (close enough to hear the whistling sound of its wingbeats) and then flew across the creek and perched in a spruce tree, still making its clear "too too too toowheep" sound and looking around, every once in a while interspersed with a "caw" or that "gling!" noise that ravens also make. Then it flew off, deeper into the forest, still calling. I couldn't help thinking that it appeared to be looking for something -- as if its unique sound was a call meant for some particular individual of its kind.