In addition to the outdoor dining areas, birds also make themselves at home around air-conditioning units. You know you have a problem if you're cleaning up after birds on a daily basis. But for reasons of food safety and aesthetics, the fewer birds, the better. Given birds' adaptability, it usually takes a combination of tricks to keep them away. Put signs on tables requesting that customers not feed the birds.
Birds perch on ledges to scan for food and predators, and for nesting.
Keep them from sitting on ledges and walls by lining the perching areas with strips of flexible blunt-tipped spikes or sticky gel. Ultrasonic recorded tapes scare birds but are nearly inaudible to humans. Playing distress calls from the particular breed during restaurant downtime also works.