IOC lists at least 8 species (maybe up to 11?) that used to be lumped within Little, including Bannerman's.
But that treatment is quite old now, I believe based on
Austin, Jeremy J.; Bretagnolle, Vincent; Pasquet, Eric (2004). "A global molecular phylogeny of the small Puffinus shearwaters and implications for systematics of the Little-Audubon's Shearwater complex". Auk. 121 (3): 847–864
and detailed in the Onley and Schofield book from 2007.
These isolated island populations of widespread tubenoses are going to keep throwing up splits i think
James