Look away now if you are easily offended!
Many years ago I had a summer job working in the Fish Market in Dublin
We were plagued by seagulls
So the regular lads came up with some serious deterrents
First one was to put baking soda into several herrings and throw them onto the roof
Seagulls would swoop down and swallow them
About 5 minutes later when digestion started the seagull would explode when his stomach acid mixed
with the baking soda, usually over either Capel Street or OConnell Street, how we laughed!
Second one was to throw 2 herrings onto the roof, they would have a 5 yard length of fishing line and hooks attached to both
Two seagulls would swallow a fish each and fly off, and when the line kicked in we would
watch them pulling in different directions until they eventually fell from the sky
The final thing they did was one fish with about 20 yards of fishing line and a hook, when the seagull took the fish they let it fly off and when all the line had played out they would yank on it and watch the poor bird come shooting down from the sky
This was before You Tube and the internet so I have no vids to show unfortunately