([@CR71]) for egg yolk analysis. The chromatographic analyses were prolonged to 75 min to evaluate the presence of esters. Pigments detected in the skin were identified by the retention time, the UV spectra and from LC/MS--MS analysis. Seeds pigments were identified by retention time, UV spectra and co-chromatography with standards. No pigments were detected in the plasma.

To measure the amount of carotenoids circulating in the blood, the plasma (20 μL) was diluted with absolute methanol (1:25) and the flocculent proteins were precipitated by centrifugation at 12,000 rpm for 5 min. Carotenoids were quantified with a Pharmacia Biotech Ultrospec (Pharmacia, Cambridge) spectrophotometer at 445 nm. The carotenoid concentration was estimated as μg mL^−1^ of serum using the standard absorbance curve of lutein (Sigma--Aldrich product number 95507). HPLC of blood samples could not detect any carotenoids and the quantitative analyses of the blood sampled from experimental birds failed, again, in detecting any carotenoid circulating in the blood. Since these pigments were detected in the skin in a relative high concentration (Table [1](#Tab1){ref-type="table"}), we supposed that the diamond doves are highly efficient in allocating carotenoids to specific tissues, maintaining their blood concentrations at very low levels, not detectable with the used devises. In addition, blood levels of carotenoids could be elevated only at the time of an increase in deposition or reallocation, while we have measured them in a stable situation. We do not think that this was an artifact, for example, sample degradation is an unlikely explanation because all other blood parameters from the same blood samples yielded values that are comparable with data in the literature. Additional analyses with HPLC using different birds and solvents gave the same results.Table 1Results of HPLC analyses of eye ring skin biopsy of a male and a female diamond dove and of food provided during the studyCompoundFemale skin (μg g^−1^)Male skin (�