This may be a minor revolution in squirrel-proofing technology -- today, I smeared cooking oil on the long hanging bird-feeder that our local squirrel (see previous photograph) or one of his/her relatives has been using as a stepping stone for reaching the top storey of the feeder.
And ... the squirrel slipped off!! Not right away, I'll admit: he/she initially managed to cling to the feeder, but a moment later appeared to be struggling and then leaped down. She (I think it's a she) tried again -- but now her paws were greasy and she couldn't get up the central pole on which the feeder is fitted.
Then a stalking two-tone predator (ibid.) interrupted her attempts and she (the squirrel, i.e.) scampered off to safety.
Of course, in a couple of days the oil will have evaporated, leaving a sticky residue to which the squirrels will adhere. And soon, there will be a bird-feeder with some very angry squirrels stuck to it ...