3D reconstruction of high-resolution, micro-computer tomography (CT) scans of the thigh bone (femur) from a male Japanese quail (Coturnix japonica). The delicate and intricate trabecular bone structure within the marrow cavity of the femur is shown here. The medullary bone used to store calcium for eggshell formation in female quails is absent from the marrow cavity in males. Average length of an intact quail femur is approximately 40 mm.
Like many other birds, quails control the timing of their reproduction through a physiological process called photoperiodism. Quails are highly sensitive to day length and use this information to ensure that reproduction occurs during the most favourable season for their offspring (i.e. in the summer). Increase in day length results in a series of hormonal changes leading to greater oestrogen production and fertility. In birds, these hormonal changes also result in the formation of extensive "medullary bone" within the marrow cavity. This medullary bone is essential to supply the large amount of calcium required to form the eggshell.