Barbed wire? Can't say I've ever had that problem myself
a clip on kestrel should do it
ziplock 4 little sticks to it, one on each corner, tie some nylon fishing wire to the sticks so it sits .25 inches above the metal. Birds no longer can perch on it.
Works here on the balcony.
I'm fed up wuv birds ****ting on my landy
Then agen the wimmin around here are abit rough
Oi !!!!!
Oi !!!!!