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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

JPG-Adult male white-winged scoter JPG-Adult female white-winged scoter JPG-Immature white-winged scoter

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