Andrew May writes
Ha! I have had one of those squirrel-proof bird feeders for many years.
And for many years it has worked just as expected. Then, last week I
noticed the rate of consumption had gone up dramatically. At the
weekend I discovered why. A rather large pigeon had discovered that by
flying onto the nearby fence, then landing on top of the feeder it
would swing it enough to deposit a quantity of grain on the ground. Fly
down to the ground to eat and repeat. So at least I now know the cause.

Depending where it is, a couple of strategically placed guy ropes would
solve that.
--
Kay