Repeatability of laboratory measurements for maternally derived yolk carotenoid concentrations in bird eggs

We describe a source of variability in maternally derived yolk carotenoids that is not routinely calculated in published studies. We quantify the measurement error in yolk carotenoid concentrations that may accrue during the analysis of yolk contents from repeat extractions and repeat high performance liquid chromatography (HPLC) runs of the same egg yolk sample from free range clutches of four farm bird species in New Zealand. We show that the variability between different eggs is substantially greater than the variability between replicate yolk extractions and HPLC analyses. Importantly, our results provide confidence to researchers that technical repeatability is a lesser concern when studying the biological differences between yolk samples.