The intrauterine pH of the sexually mature bird appears to fluctuate diurnally. The changes in pH during mineralization would suggest a more complex mechanism responsible for the movement of calcium from the plasma to the uterus. The increase in intrauterine pH during the period of active salt and water transport may indicate pH is important in this mechanism. The Fourier-series, periodogram, and correlogram methods all indicate that intrauterine pH is cyclic. Furthermore, the correlogram suggests that the cycle is endodiurnal.

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