This immature Lesser Black-backed Gull (Larus fuscus graellsii) was at Timnath Reservoir in Larimer County, Colorado. It is early in its 3rd cycle (but still in its 2nd calendar year), actively molting its primaries and rectrices. This species has been increasing its population, and has become uncommon in the non-breeding season in Northern Colorado. This bird was accompanied by an adult (not shown), and both were still present three days later on 15 Oct 2010. Note that it is slightly smaller than the adult male American Herring Gull (Larus argentatus smithsonianus) next to it.