Working dead wood

When i see fallen wood around here I'm suspect of it especially if it lies beneath the tree and not put aside away from the tree in a pile. It doesnt mean it isnt good wood as storms move in and take good wood down.
I look at the end of the branch where it got severed. If the end looks like it would if you took a piece of wet sapling and snapped it in half chances are its good wood. Sometimes wood found will have been sawed and that usually is an indicator of perhaps pruning was done on a tree and the wood should be good.
Bad wood where it came off the tree usually has a look about it, the end looks soft and rotten. Ive sawn the ends of rotten wood branches off flat and you can see sawdust within.
Anyhow, what i usually end up doing to test a piece is give it a flex test if rotten it wont take much to snap it. Hope this helps you a bit.
That wood you have pictured from what i can tell looks pretty good.

If you know who owns the land have a word with the guy he may give you permission to harvest some shanks. If he does make the guy a walking stick/hiking pole it will ensure future harvesting.

I harvest all my own shanks locally when the weather permits . its more fruitful to do this cutting 50-60 shanks takes very little time and I have already earmarked where I shall do this.

In the past I have cut 50-60 in a afternoon and it will help the bush/tree it came from .Hazel grows pretty fast and is a popular source for shanks here so to keep the trees healthy it needs cutting regularly.

I would love to get my hands on some of the species you have over the pond , but I am happy with hazel its a good sound wood and the colour variation on the barks is pretty amazing depending on where its grown.

Early on, most of what I gathered had fallen away. Too many ended up having rotten portions within. I started only gathering stuff that was not lying on the ground, and looked to have fallen within a year or so.

I still collect most of my sticks from fallen trees, but I've learned to inspect them very carefully. The stress from snapping in a storm can cause long stress cracks. And, if it fell, there was a good chance there was already insect infestation and/or fungus rot.

Eventually, I started cutting some green wood. There is enough real estate development going on near me that during the past few years I've seen hundreds of acres bulldozed clean. I try to keep an eye out for areas on the verge of development, and harvest a few pieces before the trees are torn up, or get in during the demolition.

Also, around me there are a few trees that grow like weeds, mulberry most prominently, that are not damaged by cutting limbs or sapling away.

You show a long radial split in your third picture. It may or may not be a problem structurally. If the stick seems weak toss it or use it for something else.

If you decide to keep the stick you can fill the crack. There are a lot of options for filling it. Epoxy and sawdust works. It's strong and waterproof. You can use pretty much anything solid in the epoxy. I use dried coffee grounds. It dries nearly black. I see a lot of stuff filled with epoxy and crushed stones like turquoise.

You can also use different coloring agents and casting resin for some interesting effects as well.

I've only picked up a few dead sticks. Some were pretty bug eaten under the bark. There are a lot of sticks out there. If you suspect any of being weak, don't bother using them. There's plenty of good ones out there.

I like using fresh picked sticks. I know they're good when I get them.

You're fortunate to have 30 acres of trees to choose from.

Rodney