I never, ever feed any milk products to birds. They are not mammals and lack the enzymes to digest them. I also never feed soy products to them. Too risky. And not only because of the estrogen similarity, the calcium absorption or the thyroid problems but also because soy is poisonous in its natural form and needs to be processed to be consumed safely. There is something very unnatural about feeding a bird something that nature made poisonous especifically so birds would not eat it.