Some interesting ideas here.
When I was a kid my dad had a big fruit cage with plastic netting (in London) and I remember the roof of it fell in when it snowed it one winter.
These days his fruit cages are much more elaborate, I think the smallest timbers are 2x2 fence posts! Instead of plastic netting he uses steel mesh 'aviary' wire - it is designed to keep small birds in so works just as well keeping them out. My sister decided to keep budgies a while back which is where the discovery of aviary wire came from.
The only problems with my dads approach to fruit cages are:
a) it's a permanent structure
b) it looks kind of a like a POW camp
So far I've used plastic netting to make small temporary cages over my strawberries and raspberries but it's a pain getting in to harvest, next year I will need to make something a decent height with a door.....
Anyway, birds are the least of my problems!
I opted to try plastic 'mulch' (it seems to wrong to call it that) for the strawberries this year so in order to be able to water effectively I installed a dripper system first. Finally got round to taking the net and plastic sheeting off the strawberriy bed and within a couple of days some moggy had found a bare space between the plants and started digging, scattering my dripper system at the same time. On with the chicken wire frame again then - I thought I wouldn't need that now the plants are mature and cover the bed pretty well.
But far more destructive to the fruit this year has been the wind. Last year I actually thought to pick the elderberries off my tree and got quite a nice crop, this year the wind has pretty much stripped it bare before they even ripened. It wasn't birds, no purple signatures, and the branches in deep cover that don't move as much in the wind still have some.