Species, Age and Sex Identification of Ducks Using Wing Plumage

White-winged Scoter

Age Determination

Immatures of both sexes are generally a lighter brown than adult females, but do intergrade somewhat. On immatures, the tertials and tertial coverts usually have some faded fraying at their tips. Similar light-colored fraying is often present among the scapulars. The greater coverts often have much less white at their tips than those of adults and sometimes they are entirely brown.

Sex Determination of Adults

Adult males can be readily identified by the black of all upperwing feathers except for the secondaries and the outer half of their greater coverts which are white. The sharply defined black bases of the secondary coverts create a saw-toothed appearance. There is no evidence of fading or fraying on either tertials or tertial coverts. Adult females are similar except that the upperwing is a very dark brown rather than black. It may be necessary to tilt the wings and view them closely to see that they are not black. Approximately 90% of adult females have a notch-length of less than 274 mm. and approximately 90% of adult males are longer.

Wing Character	Male		Female
	Adult	Immature	Immature	Adult
Tertials	Shiny black, tips are blunt and rounded	Dark brown, tips are pointed and usually frayed		Dark brown, tips are blunt and rounded
Greater tertial coverts	Broadly rounded, black	Narrow slightly toward tips which are usually frayed; dark brown		Broadly rounded, dark brown
Greater secondary coverts	About 1/2 of exposed portion white; remaining basal portion black on a diagonal, giving saw-tooth effect	Dark brown; some white at tips, usually as round spots, but amount of white varies among individuals		About 1/2 of exposed portion white; remaining basal portion very dark brown approximately straight across
Middle and lesser coverts	Broadly rounded and entirely black	Narrow toward tips giving individual coverts a triangular to trapezoidal appearance; tips usually frayed		Broadly rounded and entirely very dark brown

Previous Section -- Surf scoter
Return to Contents
Next Section -- Common eider