Cuttlefish bone is neither a bone nor of a fish, but it is good for birds, in any case.

Cuttlebone has too much phosphorus . . .

Mr. Robert G. Black, author of Nutrition of Finches and Other Cage Birds, defends (by referring contesters to the bibliography of his text) in forums, for example, and propagates this misinformation. Dr. David J. Kersting, D.V.M. has written just that under supervision and defense of President Gerald Oldberg of the American Cockatiel Society. I even have had to correct a Wikipedia entry over this.

It is wrong, simply. Cuttlefish bone is as suitable as eggshell as a calcium source. Maybe eggshell is supplied more inexpensively and conveniently in households where eggs are consumed liberally, but nutritionally, cuttlebone is not inferior.

I suspect that the confusion arose out of semantics. So firstly, Cuttlefish bone is not a bone. Bone is comprised of calcium phosphate, typically hydroxylapatite, and it does contain phosphorus. And while on that topic, Cuttlefish are not fish. Cuttlefish belong to a sub-class of Cephalopoda, Coleoidea, characterized as being without shell or having internalized shell.

Both cuttlebone and eggshell are composed of calcium carbonate; neither contain more than trace amounts of phosphorous. The amount of nutritionally available calcium in 10 mg of either option is equivalent.

The difference between eggshell and cuttlebone is in crystal structure. Interestingly, while feeding of eggshell may seem more appropriate since the material is presumable more “native” to avians, the calcium carbonate in cuttlebone is slightly less stable. Well, in 10 to 100 million years*, aragonite settles as calcite, so on the time-scale of metabolism in aviary birds, especially Passeriformes, this thermodynamic instability cannot be regarded as any kind of advantage.




Chemical Formula
(% Ca by mass)
Polymorph Calcitic Aragonitic
Ca Bioavailability 100% 100%
Stability Most Stable Metastable

Reference: Comparative Avian Nutrition by K.C. Klasing

EDX of Cuttlefish Bone taken using Oxford EDX attachment and Inca Software at the Nano3 facility of Calit2 at UCSD.

Less than a year ago, I contacted the webmaster of the homepage of the American Cockatiel Society requesting correction of content. President Gerald Oldberg dismissed my petition and wrote “If you are a Doctor of Veterinarian Medicine and wish to write an article defending your position, feel free to send it to me for review.” I had included in the original correspondence a scanned table from The Elementary Chemical Composition of Marine Organisms.

So I enlisted Dr. Terry Martin B.V.Sc., avian veterinarian (and author of this book, by the way). In his letter which was perfection, he reiterated the facts, mentioned that this misconception is predominantly an American problem (likely due to the State-side popularity of Mr. Robert G. Black’s publications), and made some comments about obligations of publishing accurately on avicultural websites. His letter was ignored, and it shows.

*Thanks to Ian for offering correction in the comments.




~ by finchwench on Saturday, 2 August 2008.

8 Responses to “Cuttlefish bone is neither a bone nor of a fish, but it is good for birds, in any case.”

  1. May I have permission to reprint your article in our bird club newsletter?

    Joyce Baum, Editor
    Avicultural Society of Tucson

  2. I am flattered by your request, Joyce. I have sent you a printable manuscript based on this post. Thank you for your interest!

  3. “in 10 to 100 billion years, aragonite settles as calcite”
    Shouldn’t that be million?

  4. If only I had a dollar for each time I came here! Superb post.

  5. Thanks for sharing such a good thinking, post is good,
    thats why i have read it entirely

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