Dark heterochromia in adult masked lapwings is universal, asymmetrical and possibly slightly sexually dimorphic
2022
Cardilini, Adam P. A. | Lees, Daniel | Roche, Dylan | Dann, Peter | Weston, Michael A.
Variations in eye colour in birds are poorly documented. We measured and characterised eyes of 25 birds in the hand (16° × 22.5° segments per eye), using standardised and scaled images, and examined observations of 1 marked individual through time. We describe universal and extensive dark heterochromia (non-uniform colouration of the eye) in adult masked lapwings Vanellus miles novaehollandiae in our study population. Asymmetrical within-eye heterochromia has not previously been recorded for Charadridae, but in a review of images of eyes in the genus Vanellus, we found 45% of the 22 species had detectable heterochromia. There was a tendency (p = 0.051 after false discovery rate correction) for males to have slightly less black in the upper posterior part of the eye, a difference not distinguishable enough to aid sexing in the hand. We suggest standardised images of captured birds would underpin a more nuanced understanding of the occurrence of subtle heterochromia among birds, which may permit phylogenetic analyses directed at exploring possible evolution or function of such eye pigmentation.
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