| Titre : | Which colours are possible on avian eggshells? |
| Auteurs : | Kurt Schlaepfer, Auteur |
| Type de document : | Article |
| Dans : | Vogelwelt (Die) (130(2) 2009) |
| Article en page(s) : | 99-105 |
| Résumé : | The colour of eggshells is often subject of ornithological text books or is a topic in scientific studies of birds. What is lacking in most cases is an objective description or quantification of colour. Therefore, there is a need to characterise eggshell colours by applying for instance colorimetric, i.e. perceptual values. In this context, it is also of interest to determine the possible range of colours occurring on avian eggshells. For the objective description of eggshell colours, here the CIELAB Colour System based on the attributes of hue, chroma and lightness was used. It is known that only three pigments are responsible for the entirety of eggshell colours, i.e. protoporphyrin, biliverdin and zinc biliverdin. The pigmentation of eggshells can be seen in this way as the result of a colour mixing system based on three primary colours. Indeed, the entirety of eggshell colours forms a three-dimensional space being a subspace of the CIELAB colour space. If only the attributes of hue and chroma are considered, the eggshell colours can be mapped as a surface whose area is mainly determined by the position of the three eggshell pigments. Colours with the highest possible chroma values are situated on the boundary lines of this area. In order to specify this area, those eggs have to be found exhibiting the highest chroma values for a given hue. For finding such colours, egg collections are best suited. By measuring selected eggs of some larger collections, sufficient data could be gathered to determine the area in which all eggshell colours are located. As could be expected, the range of eggshell colours is confined to red-brown, olive, yellow-green and blue-green colours. Pure blue, purple and red shades are completely missing. |
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