Assertion: penguin's call | /r/HasProperty | vocal
Facets:
Source sentences:
text: As the species has no fixed nest sites that individuals can use to locate their own partner or chick, emperor penguins must rely on vocal calls alone for identification.
text: The passerine voice box (also called a syrinx) is a vocal organ located in the trachea.
text: Since they have no permanent nest sites, emperor penguins depend on vocal calls to identify their partner or chick.