Scary stuff Pete.
I am pleased this spring, so far, with simple black netting, as long as it is suspended far enough above the leaves. As you say, pigeons are so tame: I even got close enough last spring to hit one with a hoe handle, missed and regretted it when the handle broke!
This year I have netting on hoops over spring cabbage, as described by Darren (they are also in my Winter Veg book) and for the taller kale plants I knocked some fence posts at the ends of a bed and then nailed battens on top of them, making a cage which my net is just wide enough to cover from side to side, held by a few stones along its edges. So far so good, we shall see.