It's easy to spend a fortune on your parrot. You know where to draw the line with the toys and the treats, but nutritional supplements like gravel fall in a gray area that leaves you unsure.
Some Birds Need Gravel...
Birds like finches and canaries need to eat a bit of gravel or grit to help them digest seeds that have hulls on them. Those types of birds usually eat seeds whole and benefit from having hard, insoluble grit in their tummies to wear the hard, fibrous coating away from the seeds in order to digest them. This is why many people provide grit or fine gravel for their birds to eat.
...But Not Parrots
It doesn't matter what type of parrot you have, from parakeets up to indigo macaws -- no one in the parrot family needs to eat grit or gravel to help with digestion. Hook-billed birds usually shell their seeds before eating the tasty, nutritious center so their digestive enzymes can go right to work. Additionally, pellet diets are popular for feeding parrots, and since pellets don't have tough, indigestible shells, the need for grit is even less of an issue.
Gravel Problems for Parrots
Because the outlet from a parrot's stomach into his intestines is smaller than in other species of birds, passing grit and gravel can become a problem for him. Gravel that doesn't move through a bird's system can become trapped and impacted. This can lead to other health issues like malnutrition, kidney failure and pancreatitis.
Organic Exception to the Rule
While insoluble gravel made of sandstone or silicates can cause problems for your parrot, there are organic, soluble forms of grit he can safely eat that will provide nutritional value. This kind of grit comes in the form of limestone, crushed oyster shells and cuttlebones. Soluble grit provides calcium to your bird, but you should avoid feeding him soluble grit if you don't know that it comes from a safe source. Grit that originates from regions with polluted water has been associated with heavy metal toxicity in birds.