Changes in Structure of Head Feathers of Wild Plumage Type: Male Mallard Ducks (Anas platyrhynchos var. domesticus) Following Seasonal Plumage Changes

Abstract

Seasonal changes occur in the plumage of male mallard ducks, and this phenomenon is referred to as seasonal dimorphism of the plumage. However, no information is available, especially morphological, about the mechanisms that control these changes. The present study was conducted to study the morphological changes in the head feathers of mallard drakes. Samples were collected from a total of 43 drakes from April to August, 2002. About 100 to 200 feathers were randomly extracted from the occipital region of the head. The collected head feathers could be classified into two main types ; the nuptial plumage type and the eclipse plumage type. It was observed that the whole feather (rachis, barb and barbules) was heavily pigmented in the nuptial plumage type feather, whereas pigmented and non-pigmented areas gave a dotted-line appearance in the barbs of the eclipse plumage type feather. The plumage type could therefore be distinguished by the proportion of nuptial and eclipse plumage type feathers. The length of the feather and proportion of nuptial plumage type feathers also decreased seasonally from the nuptial plumage to eclipse plumage. It was found that the length of the barb and barbules showed similar seasonal changes. These findings suggest that different mechanisms regulate the color and length of the feathers. The nuptial plumage showed significantly longer feathers, barbs and barbules than those of the eclipse plumage.

Keywords

• mallard duck
• seasonal dimorphism
• plumage
• pigment
• feather structure