Believe it or not, we get pelicans here too, in the middle of Kansas... The center of the continental US... there are pelicans and seagulls. xD The nearest ocean is like, a million miles away, and we have seabirds chillin' here.
You have rivers, probably? 
reservoirs and landfills. The Pelicans hang out on the artificial lakes, and the gulls populate the landfills.
Aha, makes sense