I've had various enclosures. The first was covered with small mesh galvanized hardware cloth for both birds and hail. It worked well but was expensive.

I now have a greenhouse which foils birds, freezes, hail, coons, etc.

Also have grapes covered with 30% black woven polypropylene. It's great stuff and can be supported with single wires about 10ft apart. But does take a fairly strong support system.

The best I've seen just for birds is linked below. Light weight and looks great!

Here is a link that might be useful: bird netting support system

That link was really useful. What a great system that fruit grower set up! Could anyone comment on this particular netting and any problems with birds or other critters tangling in it? I am asking because I have purchased cheap plastic "bird netting" elsewhere and been horrified to find various birds and harmless species of snakes tangled and dead in it. I don't want to repeat that mistake.

Thank you Fruitnut. I love your greenhouse.

I especially like the link to the place where the man got his netting. They actually have metal netting too. Since I am wanting to make a permanent structure, that will be perfect.
The problem is always getting the widest netting possible for the roof and then having supports for it. The sides are easy.
We just finished a 25' X 50' X 8' tall garden enclosure using steel and concrete. I am hoping to find a way to not have to put pipes across the "roof" or at least not as many pipes.
The man in the post did give me an idea. He has some eye bolts in parts of his uprights. Nothing is attached to them but I am wondering about using tension wire for the roof spans.
I already purchased 600 feet of 1 5/8 schedule 40 galvanized pipe. It is pretty heavy duty stuff.

My frozen, I had the same experience as you. I hated catching things in my bird netting. The biggest thing was a 8 foot long coachwhip snake. He was dead when I found him or I don't know how the heck I would have gotten him out of there. Poor thing.

mom:

I believe there is something attached to the eye bolts, 80 lb test monofilament fishing line. That supports the bird netting.

I think you are right on the line.

I was looking at some of your (Fruitnut) posts and you gave me an idea. You had a post about hail damage so I started looking at hail netting. I think it could work for my roof.
Here's a link that shows how it can be used. There are lots of companies but this one had a good picture. I even found one where you can put in a smaller order.
You can leave it up all of the time and it has a 10 to 15 year life span.

http://sinonetting.com/product/Anti-Hail-Netting.html