Just to make a point here, natural sunlight doesn't provide Vitamin D to the body, it ACTIVATES the Vitamin D that is already in the body (specifically Vitamin D3)...That's why most Calcium supplements for animals/birds also include added Vitamin D3, so that then the Vitamin D3 can be activated by the UVB light in natural sunlight. And then the activated Vitamin D3 allows the body to be able to absorb and use the Calcium.
All living creatures need Calcium because basically every body function/action/process requires Calcium to happen, right down to the cellular level. However, there are certain animals that actually need to be given an added, artificial source of Calcium and Vitamin D3 when they're kept in captivity and not in their natural environment, because their diets in captivity do not contain enough Calcium or Vitamin D3 to allow them to absorbe and use the Calcium they are getting...Most of these animals are Reptiles and Amphibians, and does not usually include birds.
The only time you want to give your bird an actual Calcium "supplement", as opposed to simply providing them with both a Cuttlebone and an Avian Mineral Block, is if they are diagnosed with a Calcium Deficiency through blood-work. And this goes for female birds that you're breeding as well; female birds need extra Calcium if they are making/laying eggs and feeding baby chicks, but not from a Calcium supplement, simply adding a Cuttlebone and an Avian Mineral Block to their cage at all times is more than enough Calcium and Vitamin D3 to allow their bodies to use the Calcium, when given in-conjunction with their regular daily Avian diet of a healthy, low-fat, high-protein Avian pellet or seed-mix combined with a serving of fresh Veggies and Dark, Leafy Greens each day as well.
So unless your specific bird actually had blood-work done and your Avian Vet diagnosed him/her with a Calcium and/or Vitamin D Deficiency, then you shouldn't be giving him/her any type of Calcium supplement at all, you just need to make sure they always have access to a Cuttlebone and a Mineral Block made for birds, along with feeding them a healthy Avian diet that is supplemented with fresh Veggies and Dark, Leafy Greens, which are very high in Calcium and Vitamin D3...If you give a bird an actual Calcium supplement in addition to their regular staple-diet of pellets/seed-mix, their fresh veggies and dark, leafy greens, and a Cuttlebone and Mineral Block, when they don't actually have a health/medical issue that is causing a Calcium Deficiency, you are likely going to cause your bird to develop a Calcium TOXICITY, which will cause all kinds of serious health conditions including everything from chronic Bladder/Kidney Stones to hardening of the Blood-Vessels in the Kidneys to actual Kidney Disease, along with many Neurological conditions that are caused by an excess of Calcium being absorbed by the body.
***So the bottom-line is that even if you're planning on breeding your female bird(s), none of them should be given nor do they need an extra Calcium/Vitamin D3 supplement. Instead, simply make sure that they always have access to both a Cuttlebone and an Avian Mineral Block, and make sure that they are getting a large portion of fresh Veggies and Dark, Leafy Greens each day in addition to their regular daily staple-diet of either a high-quality, low-sugar, "Natural" Avian Pellet or a low-fat, high-protein, varied Avian Seed-Mix. And if you're actually concerned that your birds do have a Calcium-Deficiency (they shouldn't unless they are suffering from other health issues/conditions that would cause it), then you certainly do not want to just start giving them a daily Calcium Supplement; you need to instead take them to either a Certified Avian Vet or Avian Specialist Vet, voice your concern to the Vet, and have them run full Blood-Work to determine whether they actually do have an issue. And if they did have a Calcium-Deficiency, the Avian Vet would prescribe them a high-quality, medical-grade Calcium and Vitamin D3 supplement, either by injection (usually) or by sprinkling it on their food, one such as Calcivet. But I highly doubt that your birds have any reason to need a Calcium supplement, because they would be suffering from lots of signs/symptoms and you'd know something was wrong.
Also, realize that if you were to just start giving your bird some kind of extra Calcium supplement, 99% of it would be excreted in their Urates because #1) Unless they have a deficiency they don't need it and are getting more than enough Calcium from their diet and any Mineral Blocks/Cuttlebones, and if their body can't use it, it's just excreted in their Urates (their form of Urine, the white part of their poop), which can cause hard, chalky Urates and this is how Bladder/Kidney Stones happen, and then #2) Any extra Calcium you give them must also be combined with extra Vitamin D3 and then also UVB light in order for it to be absorbed and used anyway. But again, unless your bird has some type of health/medical condition/disease that causes a Calcium or Vitamin D deficiency, they don't need it and won't absorb it or use it, and it will only cause them health/medical issues...