As for nut thieves: the Jays "harvest" my 2 trees before fully ripe (ripe brown and easy to roll out of the green cover). I have lots of new hazel trees throughout my orchard and in the loaving shed due to Jays planting them. I have been re-planting them mostly in my developing hedge rows.
As to ripeness, i gather the ones the jays drop to the ground as soon as I can otherwise mice and voles are WAY too well fed. These ones that have started to brown seem to not shrink into nothingness, but I know of what you speak: I've had that happen with ones i've picked earlier than the Jays (thinking I would beat them to the harvest; HA!) I dry them on my soil sifting racks (hardware cloth on a wooden frame), covered by another sifter so the mice and jays don't steal them from the loafing shed. I rub off the husk when they are dry and then store them in a moderately heat/cool tempered room (I don't have a commonly temp-controlled room as I live rather primatively). I've had some of them for a couple years before shelling and the majority are still tasty, solid nuts.
I long to learn how others keep the jays off: I don't mind sharing my various harvests, but I do want a sizeable portion of my goodies.

These images on Google photos don't seem to show up correctly; sorry