We’ve talked a lot about a complete and balanced diet for producing and maintaining healthy finches, but should also point out what does not belong in the diet. I hope no one gives grit to their birds. Not only does it not serve a purpose with finches, but it can be potentially dangerous and taking that to the max, fatal.
All birds are not created equal, and the finch, belonging to the most advanced form of bird, the Oscine Passerine, eats and digests food in a strikingly different way, compared to old world birds--such as poultry--from which we get old school methods of taking care of them, and that information is sometimes misleading and counterproductive.
The purpose of grit, which is a non-soluble rock—quartz or granite—is eaten by some birds, which ingest seeds, inert hull and all. They need a grinding tool to remove the hull to get to the edible kernel. Our smart finches remove the hull before ingesting the kernel, which is evidenced by all of the hulls left in the seed cups.
If you provide grit for your finch, and it eats it, it’s the same as kids eating stones, and you certainly wouldn’t feed your kid a plate of stones for lunch. If there isn’t enough food present, finches will eat it, if available, and it can become impacted in the GI tract. Worst case is a blockage and they starve to death. Sand in is sand out. It is wasted time and energy for the bird to eat it and wasted space where there could be digestible food.
If you feel by taking the grit away from your finches, you are depriving them from one of their regular foraging stops (your emotions projected onto them), then take that grit cup, clean it out of every piece of grit and replace it with crushed oyster shell. Oyster shell is pure calcium carbonate, somewhat dissolvable in the finch intestinal tract and gives your finch a minor added source of calcium. True Grit is a movie, not a finch diet aid.
Gulf Coast Finches