 However, the number of rectrices in the ducks is variable, with many mainland pintails also having 16 rectrices and a few South Georgia pintails even having 18, and the three ducks are now usually lumped as the yellow-billed pintail.The duck is a distinctive small, mottled, predominantly brown pintail.It is smaller and stockier than the remaining mainland subspecies ("A. g. spinicauda"), with more uniform and darker plumage.