Why would flares be fired into the air after a flight lands? On Monday 23rd September at about 14:30 BST my plane landed at London Stansted. Soon after landing, while the plane was at the end of its deceleration, I noticed what appeared to be two flares or fireworks shot about 50 ft into the air above the grass to the right of the runway (I believe it was runway 22).

What on Earth could that be about? The flight was Ryanair FR587 (and the plane's registration was EI-DYL if anyone is interested).
I know that flares are used at Dover air force base in Delaware sometimes to deter birds from the airfield. I also know that flares are just a common bird deterrent anyway. So it may have been simply to clear the taxiways and runways of birds before the next departure or arrival.