It is what it is. What worked for me one time was a green or red animal spray on the rump. Think the Germans use it. As far as I understand, BOP are attracted the white part before the tail feathers. Any way, in my location out in the country I have eliminated most of the usual BOP. Marsh harriers, red tailed hawks, bald eagles still around but no threat. Had a Cooper hawk or two around earlier this year. Chased the old birds. Cannot catch them in level flight. Peregrine is an ambush bird. Fortunately here the birds in the aviaries dis-pear at the sight of a winged predator. Peregrines also cannot catch a pigeon in level flight. Not here. So open the birds are fully aware of any threat. Have used hawk traps for Coopers as they always return to a kill. Peregrines, double barrel 12 gauge. If I do not hit them then scares the shit out of them.