It is not possible to confuse the White-headed Duck with any other species in the Iberian Peninsula. The characteristic shape of its beak makes this species very recognizable.
It is possible to find adult male specimens in two phases. The individuals in the clear phase have a white head with a black spot on the top (crown). The white of the head ends in a contrasting black color that fades as it goes down the neck in brown and blackish colors. The chest is brightened in chestnut colors with a cinnamon-brown back. The lower part of the chest turns into gray tones. The adult male has white underarm feathers. These specimens have an intense blue-maya colored beak during the breeding season and gray in autumn and winter. Dark phase adult males can have a completely black head. The belly would be a darker brown color, the undertail feathers darker, and the underwing coverts would not be gray but more chestnut-blackish.
The males in eclipse plumage lose the black colors of the throat area, making them resemble the females quite a bit. The neck area blends into brown colors.
On the other hand, adult females can also be seen in two phases. Clear phase females have a black crown more extensive than in the case of the male (reaching the bottom of the eyes, auricular area). At the end of this black area, they have a narrow band of off-white color that extends from the beak towards the nape. Just below, a similar band of blackish color begins. The bottom of the head (throat) and neck are white. The upper part of the chest is reddish brown, not as striking as in the male. Dark phase females have the crown, the back of the neck, and the dark band on the sides of the head a dark brown color, with the tips of the feathers chestnut.
The females in the nuptial stage have darker cheeks than in the eclipse stage.
It is possible to recognize 3 different ages:
Juvenile specimen: Two phases. In clear phase specimens, the head stands out for its dark brown colors among which the ear line stands out in a brown-grayish color above another band of the same color as the crown. In the dark phase, the head stands out for its dark brown colors among which only the ear line stands out.
2nd year specimen: both sexes are very similar to adult specimens. In the case of the sub-adult male, he still retains dark feathers in the face area. Very worn flight feathers, previous generation.
Adult specimens: DEFINED IN THE SEXING SECTION.
Adult White-headed Duck undergo a partial prenuptial molt in most cases (something that is still being studied). Few specimens undergo a complete prenuptial molt. This molt usually begins in the middle/end of February or the beginning of March. The post-nuptial molt is complete, carried out between the months of August and September. In this change process, they start with the primaries and secondaries and end up losing all the flight feathers, so they would lose the ability to fly between two and three weeks.
Primaries: 10 per wing.
Secundaries: 15 per wing.