If they don't like the oyster shell, & you can't keep up with the crushed egg shell, you could also try giving them broccoli or kale. Dandilion leaves also have a lot of calcium in them
My birds absolutely love the dandilion when it comes up, and they devoured my broccoli before I could even harvest it
I haven't tried the kale, but its a close relative to broccoli....
Yogurt is also a good source of calcium. My girls are pretty funny to watch when they eat the yogurt because they'll get it all over their beaks & then shake their heads (getting it all over everybody else)
and then they wipe their beaks all over the grass.
I did feed mix cricket feed into their food. We had frogs, so rather than constantly buying small amounts of crickets, I'd buy 100 or so & feed them. Well, we got rid of the frogs & had almost a whole bottle of the cricket feed. Its pretty high in calcium (in order to provide the frogs with calcium), and it is mostly grain products. The one problem with it is that its a very fine powder, so I don't know how much the girls actually ate.
My girls will occasionally eat the oyster shells, but they end up spilling more of them than they eat.


Yogurt is also a good source of calcium. My girls are pretty funny to watch when they eat the yogurt because they'll get it all over their beaks & then shake their heads (getting it all over everybody else)

I did feed mix cricket feed into their food. We had frogs, so rather than constantly buying small amounts of crickets, I'd buy 100 or so & feed them. Well, we got rid of the frogs & had almost a whole bottle of the cricket feed. Its pretty high in calcium (in order to provide the frogs with calcium), and it is mostly grain products. The one problem with it is that its a very fine powder, so I don't know how much the girls actually ate.
My girls will occasionally eat the oyster shells, but they end up spilling more of them than they eat.