South Polar and Great Skuas: the timing of primary moult as an aid to identification

By Dick Newell, Steve Howell and Dani López-Velasco Abstract The plumages and moult cycles of immature large skuas are poorly known, and some first-year Great Skuas Stercorarius skua can closely resemble some South Polar Skuas S. maccormicki. The most challenging birds are dark individuals in August-October with no active primary moult, and faded/moulting birds in May-August, which may be eith...