How low was “low normal”?
Low serum calcium is not usually a function of lack of adequate calcium in the diet, but rather, a recuction in the absorption of calcium into the system or a lack of efficient conversion of dietary vitamin D to active D3.
This may be due to an underlying low-grade GI inflammation problem. This may be caused by many things, including invasion by bacteria, yeast, or parasites, systemic disease causing a slowdown in GI motility, or plain old stress. Stress can affect the ability of the GI to derive nutrients from the food. The former may be from a lack of vitamin D in the diet or kidney disease.
In the case of low serum calcium, it is, of course, a good idea to supplement with a quality souce of calcium, but it is also important to investigate and rule out any other possible reasons for the possibility of poor absorption or other GI problems.
The best way to supplement calcium is by feeding foods rich in it, like dark green leafy vegetables, like broccoli, collards, kale, etc. Also, if you take a cuttle bone and scrape it, you will get a pure cacium carbonate powder that can be added to any wet food she will eat.
Also, the kidneys are responsible for converting the dietary vitamin D to the active D3, so specifically investigating their health is important.
This conversion can also be made in the skin in response to ultraviolet light (as reptiles do), so while this is not an important pathway normally, if the serum calcium is low, it may be beneficial to supply this ultraviolet in the form of full-spectrum lighting. See my previous posts on this subject for more detail.
Seizures due to hypocalcemia are not as common as the literature would suggest. It happens most often in older African greys, but we do not often see this in practice. The body is very good at mainaining calcium balance to avoid this. The parathyroid glands secrete a hormone that causes calcium to come out of the bone into the bloodstream when calcium gets low and thus prevents muscle contracile irregularities in all but the most severe cases, so I don’t think Sally is at risk for this with a "low normal" level.
Let me know how her follow-up goes.
Also, THANKS very much for the book!! I find it a great addition to my collection of "old" avian literature – I also LOVE the bookmarker that was in it. I will really treasure it!