Songbirds do not create long–term stores of calcium in their legs prior to laying: results from high–resolution radiography

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Abstract
We prepared high–resolution radiographs of the leg bones of three passerine species using X–rays at the Cornell High Energy Synchrotron Source (CHESS), which allows imaging with exceptionally high contrast and resolution. In studies of living Tree Swallows before and after laying and in studies of Brown–headed Cowbirds and Great Tits collected before, during or after laying, there is no evidence of calcium storage in the leg bones. By contrast, Great Tit nestlings raised in environments with extremely low calcium availability exhibited calcium deprivation in the development of their leg bones.