Abstract
We compared measurements and colors of feathers between male and female Long-billed Plovers Charadridus placidus during the breeding season at the Toki-river in central Saitama, Japan. The female has a greater body weight and slightly longer natural wing length than the male. The male bird had slightly wider forehead black band feathers than the female. However, measurement values of these parameters overlapped between the two sexes. The color of the forehead black band, ear part feather, and underside eye feather differed significantly between the two sexes. The male's feathers were more blackish in color, while the female had feathers that were more drab in color or that had a color similar to its body feathers “olive-brown.” Although these colors also overlapped between the two sexes, it is helpful to enhance accuracy of determination of sex, use together measurement values.
