Chickens Dieing

We have chickens for the first time and we are trying to have them be more or less self sufficient. We got them back in March and they have been outside now for 3 weeks. We have started to ween them of store bought feed and they seem to be scratching good for food. My concern is we have lost to chickens in the last 3 days and I don't know why. We had 12 chickens (now 10) that range on an area 25X50 for one week then they move to the next 25X50 area. They will rotate on 5 paddocks. The night time coop is basically 4' X 4' with 3 roosting ladders and 3 nesting boxes. Any thoughts on what might be happening would be greatly appreciated as I would like to not lose any more.

We really need more info... Did they all die at the same time? What time of day did they die? Any marks on the bodies or signs of stress? How was their water supply? What happens if you give them more food? Do they have shade during the day? How cold is it getting at night? How hot during the day?

I will do my best to answer these questions. No not at the same time, one died on Friday night Saturday morning, not sure exactly this one may have been left outside over night. The other one died in the coop last night. I did not see any signs of stress or marks. I believe the water supply is good, they had plenty of water. They have plenty of shade as their runs are in the woods. and the temperature has been between 45 and 80. Haven't tried giving more food at this time. What I was doing was taking the food away during the day and giving it back at night until last night which was the first night without food in the coop. I hope this helps. And thanks for any input.

I wonder if the birds are not yet full grown yet? Young birds will often pile together on a cold or wet night to stay warm, and the ones on the bottom or in the corner can smother to death. If they have an enclosed dry night space this probably isn't the case, unless for some reason they aren't using it. Are the surviving birds bony and lightweight? They could simply be chronically hungry.

That coop sounds extremely small for that many birds.
How is the ventilation? Is there at least one open side?

What breed are they? If they're a meat type (cornish rock) that could explain it. They just die sometimes.

If you are keeping them in a run you shouldn't take away their food to force them to scavenge - they'll seek out other food with or without "store" food available, and if they aren't really free range you risk forcing them to eat things that may be poisonous. Truly free range birds can cover enough ground to be able to eat a balanced diet but captive birds cannot do that and need the food there. When we put our chicks out they start in a pen and we leave food for them all day. They also learn to eat bugs, worms, grass, etc. By the time we let them out they're good at ranging and don't need much food but we do give them some daily.

I agree with what has been stated above. Not enough room in the coop for that many birds. Food left in the coop at night does not help...chickens don't eat at night. If you want to encourage foraging, feed each evening before they coop up and that way everyone goes to bed with a full belly.

Examine stool...bloody, runny? If so, could be cocci as they are out on the land for the first time. If you've kept them inside all this time, they have not had the chance to develop any tolerance to cocci that may be in the soils.

Ventilation in a 4x4 space would have to be incredibly good ventilation to help 12 birds stuffed into less than half a foot of space for each bird, even with roosting space available.

Try some mother vinegar in their water, open up that coop and get some air flow and floor/roost space and give them some food. Paddock foraging isn't the same as free range and all the available nutrients for 12 birds may not be contained on that small of a space, no matter how often you rotate through. Different forage/range has different capabilities and what works on one person's land may not work on another.

Switching them from a grain based diet, no exposure to soil pathogens, and brooder life into a small coop, small amount of forage, little chance of eating the feed, little ventilation, sudden exposure to soils,etc. may be the causes of your bird's demise.