Much of the confusion around grit comes from one word covering two materials that do entirely different jobs. Until those two are separated, keepers end up arguing past each other, with one side defending a calcium source and the other questioning a grinding stone. Separating them turns a heated debate into two calmer questions: does this bird need a soluble mineral source available, and does this bird need insoluble stone at all?
Soluble Grit: The Calcium Side of the Bowl
Soluble grit, usually crushed oyster shell, dissolves in the bird's digestive acids and supplies calcium and trace minerals as it goes. Because it breaks down, a bird cannot accumulate it in the same way, and keepers who offer it generally let the bird self-serve from a small separate dish, taking more around laying and less at other times. Cuttlebone serves a similar soluble role for many cage birds. This side of the grit question is comparatively settled: a separate dish of oyster shell for doves and pigeons is a mainstream practice, the bird regulates its own intake, and the material is gone once digested. Confusing this with stone is where most misunderstandings begin, because advice written about shell is often quoted as if it covered crushed rock too.
Insoluble Grit: The Argument Over Crushed Stone
Insoluble grit is small crushed stone that does not dissolve. It lodges in the gizzard, the muscular grinding organ, and is said to help mill hard food. The case for offering it rests on how doves and pigeons eat: unlike parrots, which hull seed with the bill before swallowing, doves and pigeons take every seed in whole, husks included, so everything arrives in the gizzard intact and needs grinding there. Wild birds pick up small stones as they forage, and traditional loft keeping has offered stone grit for generations on exactly this reasoning. The counter-concern is about captive conditions: cage and aviary birds often eat softer, more processed diets than wild birds, some individuals gorge on grit when it is first offered or when they feel unwell, and vets describe worries about the crop or gizzard becoming overloaded or impacted with stone that the bird took beyond any grinding need. Both positions are held by experienced keepers, which is precisely why this is a debate rather than a rule.
Reaching a Decision for Your Own Birds
Because the evidence cuts both ways, resolve the question for your birds specifically rather than adopting a loft-wide slogan. Note what your doves and pigeons actually eat, since a bird on a largely whole-seed diet is the bird the traditional argument was built for, while a bird on soft foods sits closer to the counter-concern. Raise insoluble grit with an avian vet who knows your birds, ask what they advise for that diet and species, and follow the answer you agree together, whether that is a small measured dish, occasional access, or none. If you do offer stone, present it in its own dish rather than scattered through seed, watch whether any individual bird gorges on it, and mention grit at every vet visit so the decision gets reviewed as diets change. Keep the two dishes visibly separate, and labelled if other people feed your birds, because shell tipped into the stone dish, or stone mixed through seed, quietly rewrites the decision you made. Write the agreed rule down where every feeder will see it in KinsLe, since Care Teams lets you attach the grit instruction to the feeding duty itself.