Mine wouldn't touch the oyster shell. I dry and then crush up egg shells from my chickens to feed to the chickens and the quail, but the quail dont really care about it either so i dont bother giving it to them that often anymore... if i notice thin shells i will add it back.
I do supplement with chicken vitamins in the water twice a week and feed herbs like parsley and spinach as treats, which are both high calcium food, especially dried parsley but mine prefer fresh. My egg shells are very hard it seems to be more than adequate... they also like tuna and sardines, canned salmon, when i eat those things then the quails and dogs get some too.., but not very often, mostly the spinach parsley and other herbs is what the quail want.
Heres some stuff from the internet about calcium:
Among the top 20 calcium sources: dried parsley (1468 milligrams per 100 grams),
sesame seeds (975 mg/100g),
chia seeds (529 mg/100g),
boiled lamb’s quarters (258 mg/100g), and sunflower seed flour (114 mg/100g).
Dried parsley had more calcium than even dolomite powder, a calcium mineral supplement. Fresh parsley has 203 mg/100g.
Other herbs and vegetables from the Richters catalogue with high calcium (100-300 mg/100g) are vegetable amaranth, cooked dandelion greens, mustard spinach, balsam pear, roselle, and watercress.
https://www.myfooddata.com/articles/high-calcium-vegetables.php
https://www.google.com/amp/s/www.globalhealingcenter.com/natural-health/foods-high-in-calcium/amp/
And heres another pretty good chart that lists alot of foods
https://www.ucsfhealth.org/education/calcium_content_of_selected_foods/
https://www.anneshealthykitchen.com/top-50-foods-that-contain-the-highest-amount-of-calcium/
Sorry to put so many links i couldnt find one that satisfied me so i put several!