How do I know if my chicken eat enough?

I have 4 layers, 4 youngsters and a rooster. They live in the one acre fruit orchard. It was the only area which was already fenced so I placed them there.

They spend an inordinate amount of time with their beaks in the ground, poking and digging. I do feed them a bit too - porridge, seeds, eggshells, cooking scraps and the like.

Can I trust that they find enough food in the orchard? They run like wold cup spriters to me every time I enter, as I always have some goodies for them.

If any hint of green vegetation exists in the orchard, they receive adequate food.

Chickens always act like they haven’t ate in days

It's great that they associate you with food. That makes it easier to work with them - you are The Food Bringer!
Chickens are always hungry. If you listen to them, you never feed them too much.
If you give them something they find tasty and they choose not to eat it, then you either have a sick chicken or they have maxed out what they can fit in their crop.

I know people who leave feed out in hanging feeders. I know people (like me!) who supplement what they forage with prepared feed just to make sure they get enough. My chickens prefer to forage, but they won't turn down kitchen scraps or cracked corn.
If you find they prefer to eat what you offer, but don't forage otherwise, then you might worry they are getting too much from you. Otherwise, they're probably fine. Hungry chickens loose weight, start shedding feathers, and stop laying eggs. They don't grow and they cut back on any "wasted" effort like doing chicken things (wandering around, scratching, chasing each other). As long as they look healthy and happy, you're fine.

A happy chicken holds it's tail up, the degree of "up" depends on the breed. Some of them look like a "U" when they're happy, some aren't so obvious. Watch them to see what yours do.

thanks everyone ❤️
OK, they are probably getting enough:
- they wander around eating dandelion and clover leaves. The orchard is huge for 9 chickens (one acre) so they are basically living in a salad bowl.
- I get a steady 3 eggs per day from my 4 layers.
- The whole lot is pottering around all the time.

I just got worried because they search for food all the time. When I drop in, I am greeted like Santa Claus. Especially the pullets run to me like bullet trains 🤣

If you're concerned about their weight then you can always catch some of them and feel their breastbones. That's the easiest place to feel to tell if they've got the balanced weight. If it's got a nice covering of muscle and fat, then they're fine, if it's straight bone then they're too skinny. I do agree with the previous post though, if there's still grass, then they've got enough food, specifically if you add some meat scraps and grains to balance their diet.

If they have a full crop when they roost at night, they are getting enough to eat.

I have gotten wiser. All the birds have been exclusively fed commercial chicken feed. They are still adjusting to pecking their food from the ground.

the last patch of chicken were the oldest and most used to eating from the feeder... I threw some seeds to the ground, and nobody moved! They just did not realise there was food on the ground.

Then I filled a plastic feeder with the same grains and they gulped down everything in a second.

I have not fed them for a couple of days. Today a 2-pound fish I got from my river was quickly eaten. from the ground.

I guess too much of my current animal handling philosophy comes from a time when I was working with zoo employees - very briefly.
At least half of the feed prepared for captive critters, in well run zoos, is hidden in the paddock and/or in toys and used as a reward in games and training.

Because I don't train my flock, I don't hold anything back from them for training purposes. I do scatter foodstuff through the undergrowth, put it in places on the ground where they can interact with it, and put it in containers - so about half of it is in the same place every day.
I like them to have to go look for the tasty treats, be able to play with it in a chicken fashion, and be able to find it for those days when they are feeling lazy or uninspired to hunt.

I think you're doing a great job training your flock to look for other and interesting things to peck at, eat, and try. I love the idea of keeping them guessing and trying. The fish for dinner is great!

An update.
I ended up letting the chickens roam wherever they want. They came out of the orchard in my wake (they follow me because I am "Auntie Treats"), so I started leaving the fence open. We seem to be blessed - no predators. The chickens quickly took a liking to the forested part of the farm.

Yesterday I saw three of my chickens emerge from the forest with a tiny mouse hanging from their beaks. Probably raided a mouse nest. The mice were seremoniously eaten. Also, I  get more eggs than I ever dared hope. Eggs with gorgeous deeply yellow yolks.

My mind is at rest.