Last year I was completely bummed about losing my first and only hazelnuts and my big cabbage to what I believed to be one of the Scrubb jays in the yard.
I noticed that this year again, out of the three hazelnuts that I planted, only the Italian hazelnut, the Tonda di Giffona, has a couple of nuts on it. My compost pile is right next to it, so I think it's safe for the time being as it's somewhat camouflaged by straw. But one of the native filberts in the front yard (I'm lucky enough to have four native filberts in my yard) has a bunch of filberts on it, and this is the first time any of the natives has had nuts on them. So I got smart this year, and this evening I covered it in bird netting.
I also got smart about my January King cabbage this year, which is turning out to be another colossal cabbage. It's covered in chicken wire.
I think that some research into hazelnut and filbert cultivation may be a good idea.