I know I can't feed them exactly what they would eat in the wild, my point is just getting as close as possible. Surely we don't know exactly what is closest, but we do know some things that are bad. I think that's the main thing we disagree on.
With calcium, again, anti-nutrients play a bigger role than "getting enough". Plenty of people who drink milk get the RDA of calcium... yet, in third world countries where they don't drink milk, and get less than half of the "RDA", osteoporosis is unheard of. Fruits may not get you the RDA but they will leave you with plenty of calcium to use instead of flush.
Grains have been linked to so many health problems in humans that I do not believe they are healthy. Some birds are granivorous but as far as I know, mine are not. Grains are healthier than some alternatives (thus the "health benefits" of grains), because of their fiber and carbohydrate content (high = good); but if an animal is not built to eat them they have very damaging effects. Allergy issues, psychological problems, many if not most gastrointestinal problems, and fatigue are linked to grain consumption.
I believe what you say about giving them the macronutrients (protein, fat, carbohydrates) in the ratios they need. But protein from a fruit (yes, there is protein in fruit; not much but it's not devoid--there is fat also) is different than protein from a [toxic when raw] legume. Micronutrients (vitamins and minerals) are much more concentrated in raw plant foods (particularly fruits and greens) than cooked [anything] as well. This leads us back to raw fruit.
Protein is more harmful in large doses than in small ones. Have you ever heard of a bird with a protein deficiency? Humans don't get protein deficiencies unless they are literally starving or there is some reason their body doesn't absorb it right. (Even strict fruitarians do not have protein deficiencies if they eat the proper amount of calories from fruit.) Have you heard of a bird with kidney problems, cancer, heart disease (not often known until too late), egg binding or other calcium problems? These can all be traced back to excessive protein.
I do not believe in "covering my bases" nutritionally. I would not feed an elephant meat, milk, eggs, grass, fruit and wheat in order to "cover my bases" and hope it gets what it needs. It would die more surely than if I only fed it one type of species appropriate food item. NO animal is built to eat such a wide range of "food" that humans routinely eat and inflict upon other animals. They all have a niche, a few select foods they naturally eat.
I know you didn't say fruit increases per calorie, but you also didn't say it was the decrease in water that brought about the "increase" in sugar. Even if you know what you meant, I'm sure at least a few other people reading needed clarification. For what it's worth, the decrease in water also concentrates the nutrients. Dried fruit is not as bad as some other things.
I know what I say about nutrition will label me as crazy... even here, amongst crazy bird-loving people.
