A NOTE ABOUT MINERALS AND DIET FOR DOVES
Doves need calcium for egg shell production and for feeding squabs, which need it especially for producing bones rapidly. I've been told that parents physiologically will remove calcium from their own bones in order to give enough to their progeny. If this calcium is not replenished, reproduction will cease until the diet can re-supply the need; usually a matter of months.
The drain of calcium without supplement allows about two clutches to succeed before cessation of the breeding cycle. Rickets in squabs and soft eggshells are intermediate symptoms of calcium deficiency.
Salt too is a necessary mineral. Probably there is enough salt, per se, in the diet for normal needs. But the trace elements such as iodine, manganese, cobalt, etc. deliberately added to salt for livestock are also very good for doves. Granular fortified livestock salt (salt+) is what I use. While it may come in several colors, red is the usual color.
Given these two minerals, doves may reproduce continuously year round -- year after year. Calcium and salt+ consumption goes up greatly while the squabs are in pinfeathers (perhaps about day 7) until they are nearly independent at 3-1/2 to 4 weeks old.
I use "Granular F" made specifically for laying hens in commercial production. It is 98% calcium and sized just smaller than BB shot. It costs approximately $2.50 per 50 lb. bag. Livestock salt+ is similarly priced. About 4 pinches of Calcium to 1 of salt+ is the basic ratio that I use in treat dishes. A reproducing pair of doves may eat all this amount in 1 day, if they have not had any for 1-2 days previously. My doves get it every other or every 3 days, while reproducing. Those in holding get it about every two weeks.
Grit And Sand Are Not Necessary
A mineral often cited as necessary is granite grit. It supposedly is necessary to enable the doves' gizzard to grind up hard seed. My doves at the University had no grit nor sand for 19 years and remained healthy and reproducing. Also for 6 years more at home they had none. I did note that they would avidly eat grit when it was offered to those going out of the colony -- until I started using Granular F. Then I found that the doves ignored the grit after trying 1 or two pecks. Although chick size oyster shell is adequate as a calcium source, it left a "craving" for grit. This is not so for Granular F!
My doves get the "soft" pellets, either Purina Chow Checkers, or the smaller Glenco pellets for 25-50% of their diet. Grain supplements of cracked corn and milo are available daily. Weekly supplements of the small oily sunflower seed and safflower are very much desired, but learned, food supplements. The first time or two offered, they are not much eaten.
Sporadically I also give spilled or recovered millets and canary seed from my finch cages. Others say peanuts are a good learned food item also, but I have not tried them. Dandelion leaves are taken as greens too. Well, this may be too soft a diet to need grit. Anyone out there with a contrary experience?
The mineral supplements I use also work for cage birds -- finches of several species, allowing continuous reproduction in Zebra finches, society finches, silverbills, canaries, etc.