Assertion: robin's set | /r/CreatedBy | male-female pairs
Facets:
value: to maintain their pair bond
type: PURPOSE
value: most often
type: DEGREE
Source sentences:
text: The story is different in the tropics where females commonly sing, and many species engage in duettingin birds, a coordinated set of vocalizations most often made by male-female pairs to maintain and strengthen their pair bond, more common in the tropics.