Assertion: duck's duckling | /r/Desires | their mothers
Facets:
value: for a supply of preen oil
type: PURPOSE
value: to make
type: PURPOSE
Source sentences:
text: However, young ducklings rely on their mothers for a supply of preen oil to make them waterproof; a chicken hen does not make as much preen oil as a female duck, and an incubator makes none.