Tips and Ideas
Seagulls have been a nusiance around the primary clarifiers at the Green Bay treatment facility. At times the basin railings were just lined with them, just like a scene from Hitchcock's "The Birds". That many birds meant a terriffic mess from all the droppings. Apparently now and then one would eat something it shouldn't have out of the basin, and would fall over dead. No problem until some pump downstream plugged due to a gull body. Enough to gross out even wastewater plant workers.
We tried air cannons first of all, which would blast a small charge of propane. Very loud, and worked well until the birds wised up to it. Next we tried the "plastic owl" technique. No go. There's a famous photo somewhere at the plant of a seagull perched on the head of one of the owls.
Idea #3 seems to work pretty well. Stainless wire (photo above) is strung across the basin here and there, it really seems to upset the birds. Not sure if it's that they can't quite see it, or have gotten caught up by it, but it seems to do the trick.