Absolutely Gulls are soaring birds. The airport I manage is about 5 miles south of the county landfill and 8 miles north of the Gulf of Mexico shoreline. You can set your watch by their daily commute between "work" and "home". They move en mass to the LF every morning and back to the beach late in the evening. Hardly a day goes by that I don't see them thermalling.
Talk about a great place to watch thermals form and observe various types of birds working lift! The landfill is a huge generator. If you can stand the smell that is.
Our FS soaring club regularly tows to and releases over that dump. The standing joke around here is "release towards the dump and scan for any Walmart bags you see above 3000 AGL.". Seriously. More than a few times I've seen one of the sailplanes come back with a blue WM bag impaled on the TEP or pitot.