Almost all Australian parrots have access to grit. This probably horrifies all you North Americans. But before you get me up before the animal cruelty groups, we NEVER, I repeat, NEVER, see any problems with grit. My vet, President of the Australian chapter of AAV, has only ever seen two instances of impacted crops in 15 years of practice.
One was a tiel with a crop full of human hair from over preening his owner, and the other a lorikeet which had gone crazy with mango (understandable) and had a crop full of mango fibres. It is one of the great mysteries of aviculture why North American parrots are apparently so willing to get their crops full of grit and suffer impaction, while Australian birds never get this problem.
My own theory is that our birds are just more intelligent!<G> I do know that every parrot I have autopsied has had some grit in its gizzard, and I believe that grit does help the bird to more efficiently grind up the seed in the gizzard, thus reducing physiological stress. Also all wild parrots apparently have been found to have some grit in their gizzard, and I don't think they would swallow it if they didn't find it useful. I do acknowledge that grit is not essential, but I do believe it is useful. So, grit is a mystery, even RHH comment on the paradox, and the latest edition of Australia's text on bird health, "Everybird" edition, still recommends that grit be made available, which we do without problem.
I must start out by emphasizing that my comments refer only to those species of parrots I am personally familiar with, that is the Australian parrots, Lovebirds, and Asiatics. Unfortunately Macaws, Amazons, and many other species of non-Australian parrots are extremely rare here in Australia, and outside my price range to keep.
I can assure those doubting that wild parrots intentionally consume grit that, from my own observatons, they do deliberately pick up and swallow grit. I have watched flocks of Corellas, Galahs, Major Mitchells, budgies, and other species, deliberately land on sand banks in dry inland river beds and peck away and swallow sand grains. It is a deliberate action on their part. In addition we all know the incredible ability of parrots to manipulate even very small seeds with their beak and tongue, while husking and then swallowing the seed. Given that ability, it is highly unlikely that a wild parrot would accidentally swallow grit.
What is surprising is the large amount of grit usually to be found in the gizzard of an autopsied wild parrot. A Rosella for instance might have up to 50 grains of grit in the gizzard. These range in size from perhaps white French millet size, down to almost microscopic size - presumably reflecting the amount of wear that the grain has undergone. At a recent Parrot Convention held in Grafton that I attended, one talk was by an avian vet, and was a demonstration of how to autopsy a parrot. The "victim" was a road kill Galah, and it's gizzard had a pile of grit in it - almost half filled!
Birds that do not hull their seed such as finches, doves and quail have to have grit to properly digest their seed. Finches will die from starvation if they don't have grit in their gizzard. As for how the practice of giving grit to parrots started, I would think it far more likely that it was as a result of both watching wild parrots and seeing what was in the bird's gizzard when wild parrots were dissected.
Actually when an autopsy is done on a seed-eating parrot, it is surprising just how much seed seems to be swallowed unhusked. Some birds might have 20% or more of the seed in their crop which is unhusked, particularly the smaller millets and pannicums.
Parrots can certainly live their whole lives without grit. The question is whether having a significant amount of grit helps that bird to have a less-stressed (= more efficient) digestive system. I believe that it does. Anything that makes it easier, and more efficient for the bird to grind up the seed before the digestive system gets to work must be a help to the bird.
This idea that a sick bird will gorge on grit is a common one in the USA - all I can say is that I have never, ever, come across such a case. I have never seen an autopsied parrot with a gizzard full of grit and never seen grit at all in the proventriculus. I also find it incredible that a single vet in Florida sees hundreds of grit impaction cases a year, while Australian vets see none! Something is wrong here. Perhaps with USA vets not having exposure to wild parrot autopsies, they are not used to the large amount of grit that can occur in healthy wild birds. What they are diagnosing as gizzard impaction, to Australian vets might be a healthy and normal grit load for a bird.
My mention of crop impaction was solely because no case of gizzard impaction was seen, although some of the list stories from the USA do refer to crop impaction due to grit being a problem.
One could get speculative here, so here goes! While parrots can digest their food without grit, perhaps birds have indeed died from "grit deficiency". Perhaps, as some later replies have alluded to, an absence of grit might lead to a long term digestive system problem due to inefficient absorption of nutrients due to inefficient grinding of seed. Such a deficiency may never show up as a primary cause of early death, but may result in a depressed immune system, and result in a bird having an earlier death than it should have. One could speculate in all sorts of directions here, but it will remain purely speculation. Even designing an experiment to test that hypothesis is daunting, never mind funding the 20 year lifespan of a project which would involve hundreds of birds!
Some comment has been made about possible compositional differences in the grit provided. I don't believe that is of any relevance. The grit used by Australians tends to be whatever is handy. As long as it is small (about millet size) then it doesn't seem to matter, if it is quartz, crushed volcanic rock or any other rock. Some use river sand, others beach sand, and others quarry crushings. My mix - a local river sand sold by landscape yards - is probably about 75% silica, with the rest being a real mixture. As I mentioned previously, crushed shell grit is useful only as a calcium source, it dissolves too quickly, and is too soft, to be of value in gizzard grinding.
While I am happy and relaxed about giving my birds unlimited access to grit, I neither encourage nor discourage anyone else to provide grit. It is a choice that has to be made by each individual, like the choice to feed pellets or seed (or neither!). And, as always, if in doubt - DON'T.
cheers, Mike Owen Queensland Australian Rep. World Parrot Trust.
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