FORT COLLINS — I thought I might witness a landmark moment in Colorado birdwatching history at the Larimer County Landfill on a Saturday in March. It was an overcast afternoon at the county's 640-acre trash depository — basically hog heaven for gulls, which dine mostly on garbage. The fervent squawks of 400-some gulls intermingled with the distant beeps of dump trucks and scrapers. I stood behind a tall telescope, two seasoned birders stationed beside me at their own scopes.