Editor’s Note (August 2016): Maps, rich media, and text have been updated to reflect a taxonomic change/split for this species. This species account is still being edited and may contain content from an earlier version of the account.
The Band-rumped Storm-Petrel ranges throughout the Pacific and Atlantic Oceans. It breeds away from continental areas on remote islands of Japan, the Hawaiian Archipelago, Galápagos, and small Eastern Atlantic islands off the coasts of Spain and Africa. Band-rumped Storm-Petrels, originating from Eastern Atlantic breeding populations and once thought only to be blown to the North American coast by storms, are now known to be regular visitors to within 50 kilometers of the Atlantic and Gulf Coasts. In the United States, this species breeds only in the Hawaiian Archipelago, where it is the rarest and smallest breeding seabird; exact locations for most colonies in the Hawaiian Archipelago are still unknown, though evidence suggests that some exist high on Hawaiian volcanoes (from about 2,400 to 3,350 m), making this one of the highest nesting seabird species in the world. The Band-rumped Storm-Petrel is not considered threatened worldwide, though it is a candidate for listing (U.S. Fish and Wildlife Service [USFWS] U.S. Fish and Wildlife Service 2002e ) because of its very small population size in the Hawaiian Archipelago.
With twice the body mass of the Band-rumped, Tristram's Storm-Petrel is one of the largest of all the storm-petrels. It is rather sedentary, breeding only in the remote Northwestern Hawaiian Islands and small islands off Japan; at sea, it remains close to and between the 2 archipelagoes. Tristram's Storm-Petrel is considered near threatened ( BirdLife International 2000 ) as a result of population declines due to overexploitation and introduction of mammalian predators by humans.
Band-rumped and Tristram's storm-petrels are members of the family Hydrobatidae (order Procellariiformes), which contains 20 species, characterized generally by small size and dark plumage (lighter underparts), nocturnal colony attendance, burrow-nesting behavior, and seizing of prey from the ocean surface. Both are members of the Northern Hemisphere subfamily Hydrobatinae (13 species), characterized by long, pointed wings; notched tails; and legs that do not project beyond the tail in flight. In contrast, the subfamily Oceanitinae (7 species) is of Southern Hemisphere origin, and its species are characterized by short, rounded wings and legs usually extending beyond square tails.
Storm-petrels, in general, are difficult to observe, and the Band-rumped and Tristram's storm-petrels are no exceptions. To avoid predation, populations breed on remote islands and often in inaccessible places, spending the nonbreeding season far out to sea. When breeding, they fly about over the ocean by day to feed on surface plankton and return to land only after dark, when they feed their young in cryptic nest burrows. Storm-petrels sighted at sea are usually hard to identify with certainty owing to often difficult viewing conditions, reluctance to follow ships, and the close similarities among species. Flight characteristics are often the key to distinguishing species.
Owing to these difficulties, few researchers have studied Band-rumped or Tristram's storm-petrels in any detail. There are only 2 major breeding studies of Band-rumped Storm-Petrel: Allan ( Allan 1962 ; Ascension I.) and Harris ( Harris 1969d ; Galápagos Is.) Interesting, more recent work on Band-rumped Storm-Petrel discovered that populations breeding at different seasons on one island in the Azores are distinct morphologically and genetically, a possible case of sympatric speciation ( Monteiro and Furness 1998 ). Much more work remains to be done on Tristram's Storm-Petrel, for which there is only one detailed breeding study ( Marks and Leasure 1992 ). Because of the secretive habits of these species, and remoteness and/or inaccessibility of their breeding sites, estimates of populations are out of date and inaccurate, making their protection difficult.
In the following account, where not stated, information pertains to both species.