While conducting nest surveys for shorebirds in California and Utah, I’ve occasionally encountered unpigmented or lightly pigmented eggs in species such as Black Skimmers, Forster’s Terns, and American Avocets. These eggs lack the typical speckling or coloration expected for camouflage in open nesting environments. Despite extensive literature on egg morphology and pigmentation, I haven’t found published documentation on the frequency or causes of this phenomenon in these species.

Eggshell pigmentation is generally attributed to two main pigments—protoporphyrin and biliverdin—whose deposition can be influenced by genetics, diet, and physiological stress. Some studies suggest that nutritional limitations or environmental stressors may reduce pigment production, while others propose that pigmentation may serve as a mechanism for trace element regulation. However, the role of diet, habitat conditions, or contaminant exposure in pigment variability remains unclear for shorebirds.

Question to the Community: Has anyone observed similar occurrences of unpigmented or lightly pigmented eggs in shorebirds or other waterbirds? Are there known environmental, dietary, or physiological factors that might explain this variation in pigmentation? Any insights or references would be greatly appreciated.