Could someone tell me what they're so pissed off at?


    

Maybe they think small bits of that foam would make nice insulation for a nest.

they probably think it's Calcium..LOL

Maybe they were looking for a fig to eat and cursed the cup because they found no figs. ;)

Then again, are you sure it's a bird doing the damage?

They saw the styro cup full of potting mix and assumed was full of your fishing worms.

Put a styro cup out there with a snake in it.  They'll get quite a surprise when they open it.  They may think twice before approching another.. lol

Hi FMD,
They thought you left a coffee for them ?

What kind of birds is it ? Here in winter the crows will come to the gardens and lurk around for some food or game to play.
I hang eggshells in the trees ... and they eat/destroy them all . I replace the shells in the Spring and they don't touch them then.
I would simply put a stronger container around the Styrofoam cup - like a plastic bottle of milk that you would cut to fit that need .

We have a positive id,

I expect a full frontal assault by birds once figs start to ripen next month, so I built a birdcage to be swathed in bird netting.

Yup, those are the ones, Rafed, except meaner and angrier.

Good theories, everyone but I personally believe I have the orneriest birds in the country.
JD, I've seen them destroy plastic tree tags and plastic easter eggs to smithereens just for fun.
The irony is that they are the luckiest birds in the world living in an oasis of seeds, berries, and fruits (including an all you can eat buffet of figs) provided to them on a silver platter by yours truly. 

I had birds steal the plastic name tags off my grape vine markers :(

Try covering in foil, I think the birds will leave it alone.  Unless they are trying to spite you, in which case you are doomed... DOOMED... LOL.

Yeah, foil only attracts the little bastards even more.
Update: Yesterday I re-applied the air layer using a plastic cup covered with foil and then camouflaged it with a thick layer of mulch. This morning I found the mulch gone, the foil torn to bits and the cup half empty of soil
I redid the air layer once more and placed half a cider block on top of it. Let's see how the little vermin react to that.
Why do I feel like I'm in a Roadrunner cartoon?

Wow Frank... That is so not right. Good luck my friend

Maybe a rubber snake under the fig or an owl statue would intimidate them.  Or paint the Styrofoam cup with something that tastes nasty to a bird but won't poison them.

Or cover the cup with duct tape.  That should be pretty hard to pull apart.

This is Frank and one of the birds,

LOL...That's us alright, except I'm always on the losing end.

What would happen if I finally won? 
Hopefully not this!

spraying with tabasco deters rabbits, squirrels      n dogs. it burns their mouths.

not sure about beaks but if you have some around try tabaso.

Birds don't taste capsaicin.  That's why you can spray birdseed with pepper spray to deter other rodents without bothering the birds.

thanks jkuo. after my success with tree eating bunnies i'd thot of spraying figs against birds, but i guess that would be too easy.