Assertion: hummingbird | /r/CapableOf | walk fine line
Facets:
value: because of their extremely high metabolism
type: CAUSE
Source sentences:
text: When it comes to keeping enough fuel to support daily activities, hummingbirds walk a fine line.
text: Hummingbirds walk a fine line because of their extremely high metabolism, so they have only enough energy stored to get them through a night.