Don't forget that long grass policy is coupled with other matters. A good bottoming out in the March to remove all the dead grass and then a good feed to encourage strong growth with a good quality sword - this creates a nice dense grass that means the birds are unsighted to the prey in the grass and go elsewhere. The grass must be regularly topped to sustain optimum length of between 150-200mm.
Short grass, whilst practical for other reasons - creates risings which offer protection/breeding places for invertebrates. A good proactive BCU is also essential - never give them a minute and regularly use lethal force - that'll learn them.
BUT - Runways are also a hazard - just have a look at all the worms on a RW during a wet, dull morning with all the birds feeding. If you are operating LVP's with a wet RW around dawn time you are in max Birdstrike risk territory!