You mean a jet engine that is up to 160 decibels isn't enough to scare them away?
Obviously not.
Anyway, flocks of them around a runway is the scary part. Get a pair of gulls into an engine at takeoff, and things go really bad.
I once planted several hectars of Lupins around and close to an international airbase's runways. They were intended to encourage the life of foxes/minks and such. Egg-stealers and young bird killers.
It was a NATO bas and funded by NATO.
Lupins will make some scrub, making i harder to birds to sit, as well as providing shelter to foxes and alike.
I have no idea whether this worked, but at least no birdstrikes in years.
Now a squadron of migrating birds is a completely other thing. But once up to cruise, one should be safe. However, Swans have been spotted at more than 20K AFAIK, and both them and the geese will benefit from using Jetstream. So in short, the problem of possibly hitting birds is yet not so easily solved.