Colour aberration in the Western Jackdaw Corvus monedula

抄録

Colour aberration among Western Jackdaw in urban environments is being increasingly encountered and photographed. For this study individual jackdaws characterised by colour aberrations were recorded by volunteers on the iNaturalist website (a social media website). The jackdaws were classified according to a proposed scale based on the amount and distribution of colour aberration on the bird's body. Using this classification of individual jackdaws, two principal components were computed as general multivariate indicators of plumage whiteness. All individuals included in this study had a form of leucistic phenotype, with the wings showing the highest degree of whiteness. The geographic location of the records was also included in the analyses. The overall percentage of jackdaws affected by colour aberration was quite high at 1.25%. This form of research, using internet-based citizen science, is an effective way of obtaining a large sample of individuals from the entire range of a species. However, further observations and experimental studies are necessary in order to explain the causes of colour aberration in jackdaws.