Photographed 30 Jan 2010 through my telescope at Carter Lake, Larimer County, Colorado, this 1-cycle pale Kumlien's-type gull, Larus glaucoides kumlieni, exhibits dark-centered tertials, a feature of Thayer's Gull, L. thayeri. Could this be an F1 hybrid kumlieni x thayeri, or perhaps a bleached thayeri? Click on image to enlarge.