Assertion: hummingbird | /r/CapableOf | fill unoccupied niches
Facets:
value: in southern canada
type: LOCATION
value: in the u.s
type: LOCATION
Source sentences:
text: as the great ice sheets retreated from North America, they gradually expanded their ranges to exploit rich temperate food resources and nesting space, filling unoccupied niches in the U.S and southern Canada while evading intense competition in the tropics.