Maybe I will be caging them up next year.

I read somewhere that the male plant has a small, almost non-descript flower on it that grows directly on the bark.

I suggest you Google some images of catkins, female flowers and nuts so you can recognise them. Round here the nuts are falling right now. I picked up some from the pavement on my walk home yesterday. They were from an ornamental red leaved bush in hanging over someone's garden wall. Tasted fine but not quite as sweet as the wild hazels.

Squirrels will make the nuts disappear on a regular basis as will even chipmunks. I cut down my trees because I got tired of feeding rodents- the last time I had a nice stash of nuts was when I found a chipmunk cache in the ground when planting a tree. What an ingenious storage system that was.

It is hard enough to keep the squirrels from fruit, but even if there are very few squirrels around they will usually take every hazel nut before they are completely ripe.

If you grow the trees out in the open with single straight trunks that are at least 4' above the ground before the first branches occur you can build baffles to keep rodents off the trees. I think squirrels would chew through anything less than chicken wire to get to nuts so netting is probably not adequate (unless you use chicken wire).