Different pigmentary alterations of a carotenoid-based patch in the Great Tit Parus major: two cases to discuss

Alterations in bird plumage coloration such as albinism and melanism have been widely cited in ornithological literature. Some types of plumage coloration are the consequence of pigment molecules stored in the feathers: carotenoids provide the red and yellow colours; and melanins are responsible for black, reddish and brown colours. This paper describes two records of alterations in the yellow breast (a carotenoid-based colour) of Great Tits Parus major: a nestling that was probably a total albino to carotenoids; and a fledgling with melanism. Possible proximate causes of both pigmentary alterations are discussed. Plumage alterations have been well documented through an observational perspective but experimental work with these alterations could be useful in understanding the functions of plumage in social and sexual contexts.