@JLcribber but, with the smaller birds like canaries and finches - we also have to supplement with calcium (extra). Hence the question.Calcium is only one aspect of nutrition. They need all the vitamins, minerals and trace elements, along with amino acids and the like in the proper proportions in order for each of them to be utilized. If you are going to supplement a bird it must be with a "complete" supplement that provides this things.
My preferred product.
THE BEST WAY TO ENSURE TOTAL NUTRITION FOR ALL CAGE BIRDS PRIME adds 14 essential vitamins and 9 minerals missing in commercially prepared seed mixtures forhari.ca
Calcium does not absorb and therefore not utilized unless the other proportions of things like phosphorus are present.