The native or Pateros duck, commonly called itik, is the most popularly raised locally. Although smaller than imported breeds, they are good layers and non-sitters. Their eggs are large. Its predominant colors are black and gray. Some are barred (bulek), others are brown or have white feathers mixed with black/green. Males have coarer heads and heavier bodies than females. Males emit shrill high-pitched sounds. They have curly feathers on top of their tails. Females emit low-pitched quaking sounds. Their tail feathers lie flat or close to the bodies. In all commercial duck hatcheries, sexing ducklings determining the sex is done at the age of 2 or 3 days.
Excerpt from agripinoy.net