Assertion: petrel's head | /r/CapableOf | form extensive dark cap
Facets:
Source sentences:
text: Gould’s petrel has a darker head forming an extensive dark cap, and a more extensive black leading edge on the under-wing.
text: Cook’s and Pycroft’s petrels have a shorter and thinner black leading edge on the under-wing; Gould’s petrel has a darker head forming an extensive dark cap; Chatham petrel has the dark under-wing bar extending to diagnostic dark axillaries (‘armpit’ feathers).