Quantification and variability of eggshell pigment content

A high-performance liquid chromatography method was used for the determination of the eggshell pigment constituents. Using this method, the content protoporphyrin IX in seven bird species was quantified. It was found that this compound is most abundant in the eggs of the blackbird (65.55 nmol per egg), but when the amount is related to the eggshell mass, then the greatest amount is in the egg of the yellowhammer (301.0 pmol/mg eggshell), while lowest values were found in the eggs of the swift (0.59 nmol); dunnock egg shells also contained biliverdin (10.25 nmol). Eggs of the red-backed shrike show a high variability of porphyrin content (9.40 ± 6.27 nmol; range 1.03–20.61 nmol per egg). The high intra-species variability of the porphyrin content is likely to reflect physiological influences, e.g. order of egg laying and nesting conditions rather than the effect of the environment.