Description:
<jats:p>Carotenoids are essential antioxidant micronutrients. Oviparous species acquire carotenoids from their food and deposit them in the egg yolk, where they support embryonic development. The total carotenoid concentration in the egg yolk is typically measured analytically, which requires time, equipment and expertise, and can limit the sample available for other measurements, at least in species laying small eggs. Here we evaluate whether yolk colour can be used as a reliable alternative measure for total yolk carotenoid concentration. We compare two non‐analytical methods, digital photography and visual colour scoring, using eggs from a wild population of Blue Tits <jats:italic>Cyanistes caeruleus</jats:italic>. Yolk hue estimated from digital photographs correlated more strongly with total yolk carotenoid concentration measured by high‐performance liquid chromatography (HPLC) than did the visually assessed colour score based on a Yolk Colour Fan. Previous results based on HPLC measurements of total carotenoid concentration could be reproduced using yolk hue measurements. The results suggest that measuring yolk hue is a suitable proxy for assessing natural variation in total yolk carotenoid concentration in eggs of free‐living birds.</jats:p>