Sexual Dichromatism in the Blue-fronted Amazon Parrot (Amazona aestiva) Revealed by Multiple-angle Spectrometry

Abstract

Seventy-five percent of psittacine species, including the blue-fronted Amazon parrot (Amazona aestiva), are classified as sexually monomorphic. However, this classification is based on the inability of the trichromatic human eye to perceive light in the near-ultraviolet spectrum. Spec- trometry is a technique that enables humans to recognize the increased range of color perceived by the tetrachromatic avian eye. By using this technique, researchers have reclassified many avian species as sexually dimorphic. In this exploratory study, several body regions of 30 blue-fronted Amazon parrots (males and females) were investigated by multiple-angle spectrometry. A model was developed that enabled gender prediction with 100% accuracy based on plumage color char- acteristics. However, the areas that were most promising in our model (forehead and wing tip) need to be confirmed independently to exclude the possibility of type I error attributed to multiple testing.