Evaluation of a glossmeter for studying the surface appearance of avian eggs

Gloss is a striking characteristic of avian eggshells that may affect both egg recognition and clutch predation. Previously, gloss has proved difficult to quantify objectively. Newly developed handheld glossmeters seem to offer a solution. We evaluated the use of a handheld glossmeter for a range of different eggshell surfaces, shapes and sizes. In all cases, their measurements were strongly affected by egg size and seem currently suitable only for very large eggs; the size of Rhea sp. eggs or larger. A glossmeter may, however, still prove useful to quantify other structures in comparative ornithology, with flat surfaces such as feathers or nest material.