Distinguishing Black-tailed Godwit subspecies limosa and melanuroides using quantitative assessment of plumage

For two subspecies of the Black-tailed Godwit, I have developed and adapted a new method for the quantitative assessment of the density of the dark bars on the belly and the number of barred feathers in the undertail coverts for the purposes of determining their sex and the subspecies to which they belong. I studied 68 Black-tailed Godwit Limosa limosa L. skins from five subgroups in the E Europe and N Asia breeding ranges of the two subspecies L. limosa limosa and L. limosa melanuroides and evaluated the variability of two plumage features: (1) the density of the dark barred feathers on the belly, and (2) the number of barred feathers in the undertail coverts. In the limosa subspecies, the density of barred feathers on the belly of males (0.65 per cm2) was significantly greater than that found in females (0.31 per cm2). The density of barred feathers on the belly in the subspecies limosa was significantly less than that found in the subspecies melanuroides with only slight overlap in males and no overlap in females. However, the sample of melanuroides was small; therefore the development of firm criteria will require more data.