One of the things that rounds out our ecosystem is chickens. They eat anything left that we don't. Then, with a very well rounded diet, chicken poop feeds the garden.
It seems easy, right? Nature taking care of itself. Another case of the big circle of life working very well without the hand of humankind to manipulate it.
Years ago though, when we first got chickens, we fed them grain. When you first start doing something, you have to just do what people tell you to do because really, you don't have a clue.
In our second year of chickenhood, we found out that our one child, who had been mysteriously ill for three years, had a fairly major gluten sensitivity issue. So was one of my questions, 7(?) years ago when we decided to switch to a fairly grain free household (including the animals because exposure was still making the children sick), was: What food, from the earth (not a factory but the earth) is toxic for chickens.
It was bizarre how I could find lists of what was toxic for dogs, cats, etc. but not much for chickens.
Everyone I asked just said, "Well, they eat grain."
And when I would ask, "Well, what did they eat before people started locking them up and just feeding them grain?"
And they would act puzzled when I would state, "My chickens like meat the best. I know because I've watched them hunt for toads and fight over who got the toad in the end. They must eat other stuff. What else would that be?"
Even seasoned chicken people would say, "Chickens eat meat?..."
Even the Ministry of Agriculture and Food said, "Chickens eat meat?..."
No one seemed to know what chickens *really* eat. I got lists from a couple of different sources but knew that they were wrong because by the time I found them, I had been feeding our chickens everything we were eating for a couple of years. (all our scraps, leftovers from the fridge that we didn't want anymore, etc.)
So, we had to think about what they would eat in the wild... and do a lot of trial and error.
Now, they don't get a whole lump of any one kind of food... so if something is toxic, they don't get enough of it to bring on any outward symptoms. That said, everything went into the chicken pot that used to be the compost pot.
If the children didn't eat the grapes fast enough, I put them in the 'chicken pot' and they'd get thrown out with all the rest (some grapes would be quite good, while others were not but I didn't have time to pick through them). So they've had loads of full grapes with no issues over the years. And it seems to me that grapes would be a natural food for almost any bird.
I would limit raisins because of the chemicals that can be used in drying them these days but I would think that in the wild, they'd eat some of those too. Our guys have eaten them on occasion without issue (my kids liked to share their snacks with the chickens) but because of the sulphites, I've always told the children not to feed too many.
My final thoughts on grapes... if they can swallow a whole toad and break it down, I didn't even think to worry about whole grapes.
One exception was raw potato peels and tomato greens because of the solanine. If I thought there was too much, I'd pull some and throw them in the garden. The problem was, we free range our chickens during the day and they'd just go over and eat them anyway. So I stopped being so picky.
We had a dog who would also vomit if he was given any potato and after doing some reading up on them, I'm not convinced they're all that healthy for humans either (lots of joint pain issues associated with them). So now potatoes, in our house, are treats and we don't peel them, so the animals only get extremely small bits and pieces now... not enough to seem to do anything to anyone.
We've had one fatality in the last 7 years that I SUSPECT was due to food. My young daughter decided to give her young silkies (house chickens at the time because we felt it was too cool outside for them yet) the left over bacon and hashbrowns from breakfast.
(What are you doing? I said, that food is too expensive for those chickens and we could've put it in the salad at dinner tonight! And I like reheated hashbrowns, so she had just dumped MY lunch in with the chickens.)
Sadly, within about 20 minutes, the biggest one with a tendency to gorge, died. The other three, though they ate some, seemed perfectly fine. Obviously my daughter felt just horrid! (These were her first silkies, her very special chickens and she was so proud of them.)
So even still, I'm not completely sure if it was what they were fed. Nevertheless, the rule is now that bacon and hashbrowns don't go to animals (bacon is a treat in our house even for the humans because of the price, so regardless, I don't want the animals eating it). And over the years I've become a very lazy cook so we don't peel our potatoes anymore... plus we limit our own intake so there just aren't enough around to make anyone sick.
Chocolate (all leftover chocolate) in our house, is to go to the Mom (me). So though I've heard it's bad for dogs and it might have been on one of the lists for chickens, they just don't get to eat it in our house. And the kids know that if chocolate gets 'wasted' on animals, Mom will have a screaming hissy fit. :O
We do supplement with sunflower seeds when scraps from the kitchen seem low. I also supplement with cooked rice.
The most interesting thing was that when we took out raw grain from their diet, their water consumption was cut in half. They just didn't seem to need all that water anymore.
One more tip. If you use a tub big enough for watering, put some goldfish in it. It gives the chickens something to play with and since they never seem able to catch all the fish, you'll never have mosquito larvae that survive.
Again, the big circle... it just works.