How do you keep birds away from an area and maintain it that way for a long time? Surely it must be difficult, specially if it’s a large area of land.
The different methods used are explained in the two separate answers below.
Most airports have a Wildlife Management Program which identifies what sort of wildlife is in the vicinity throughout the year.
Airports are very attractive places for a great number of animals because they offer food, shelter, water and there are few to no natural predators. So you have to manage the animals that naturally exist (like turtles, raccoons, skunks, foxes, hawks, frogs, etc.) and then make the airfield an unattractive place for migratory birds and larger birds that want to nest like geese and ducks.
Our primary way of nudging unwanted birds away is with scare cartridges fired from modified starter pistols. They go off like small fireworks and make a lot of noise, and we fire off several to get the birds in the air and away form the traffic areas.
We also deal with the occasional deer or coyote, and in that case we have to open various gates and herd the animal out with pickup trucks. Worst case scenario we have a shotgun, but it’s very rare that it comes out. I’ve been doing it for 16 years and I’ve only ever used the gun twice in that time.
Ultimately, it’s the airport maintenance department which has staff routinely checking problem areas for wildlife throughout the day, every day.
I was researching invasive bird populations at a Hawaiian island, which overlapped with the area around an airport. It is definitely NOT naturally bird free and is actively managed as much as possible. It is federal land so a federal employee (usually fish & wildlife) hangs out and manages the entire facility (read manage = shoot). Everything is certified and deemed humane, and let me tell you, that guy was a damn good hunter so no creature suffered. He also was responsible for ID’ing the birds before so as to not kill any threatened or endangered ones. We actually used a lot of his catches for research, so nothing went to waste.