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

Abstract

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.

Eggshell Appearance Does Not Signal Maternal Corticosterone Exposure in Japanese Quail: An Experimental Study with Brown-Spotted Eggs

“…Thus, it is possible that CORT treatment may have affected some aspects of the eggshell matrix structure that are not directly related to eggshell pigments [34]–[36], but that might change eggshell gloss [64] and thus explain why we found a change in eggshell brightness but not in eggshell red or blue-green chroma or pigment concentrations due to the treatment. Nevertheless, neither chromatic nor achromatic visual contrasts were influenced by CORT supplementation, which suggests that the change in eggshell reflectance due to the treatment would be undetected by an avian visual model.…”

“…We did not find any significant effect of CORT supplementation on female body condition or maternal investment (i.e., in egg mass), but we cannot rule out that our treatments modified the assimilation and metabolism of certain nutrients such as calcium, an element that is fundamental to the integrity and strength of the eggshell as suggested by the structural function hypothesis [63] to explain eggshell pigmentation. Thus, it is possible that CORT treatment may have affected some aspects of the eggshell matrix structure that are not directly related to eggshell pigments [34] – [36] , but that might change eggshell gloss [64] and thus explain why we found a change in eggshell brightness but not in eggshell red or blue-green chroma or pigment concentrations due to the treatment. Nevertheless, neither chromatic nor achromatic visual contrasts were influenced by CORT supplementation, which suggests that the change in eggshell reflectance due to the treatment would be undetected by an avian visual model.…”

A nanostructural basis for gloss of avian eggshells

“…To minimize geometric rsif.royalsocietypublishing.org J. R. Soc. Interface 12: 20141210 variation associated with shell curvature, which can affect measurement of gloss [42], we took measurements from the flattest part of fragments taken from the equatorial region of eggs. We measured specular reflectance between 108 and 508 from coincident normal at 58 increments using a spectrometer equipped with two fibres that rotate independently from one another; one fibre was connected to a light source (AvaLight-XE pulsed xenon light) and the other fibre to a spectrometer (AvaSpec-2048 spectrometer, Avantes Inc., Broomfield, CO, USA); our equipment set-up did not allow us to take specular measurements at angles below 108.…”

Morphological basis of glossy red plumage colours

“…Gloss has been studied in human hair (Keis, Ramaprasad & Kamath, 2004), synthetic material (Wicks, 2011), eggs (Igic et al, 2015;Maurer and Cassey 2011), plants (Vignolini et al, 2012), and feathers (Toomey et al, 2010;Maia et al, 2011). Glossy surfaces in all these cases are typified by high specular brightness.…”