QUANTIFICATION AND VARIABILITY OF EGGSHELL PIGMENT CONTENT

A high-performance liquid chromatography method was used for the deter mination 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 blackbir d (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 th e swift (0.59 nmol); dunnock egg shells also contained biliverdin (10. 25 nmol). Eggs of the red-backed shrike show a high variability of por phyrin content (9.40 +/- 6.27 nmol; range 1.03-20.61 nmol per egg). Th e high intra-species variability of the porphyrin content is likely to reflect physiological influences, e.g. order of egg laying and nestin g conditions rather than the effect of the environment.