On 13 August while helping lead a Santa Clara Audubon Society pelagic trip to the Farallon Islands, Matthew Dodder and Bob Power found a Pterodroma petrel fitting the description of an ABA Code-4 Hawaiian Petrel (Pterodroma sandwichensis) located 8.67 miles, south southwest of South Farallon Island in a large shearwater flock. Images of the petrel can be found at
http://birdingpix.blogspot.com/
Because of its similarity with Galapagos Petrel (Pterodroma phaeopygia) and because there currently isn't a specimen to examine from the ABA Area, the ABA Checklist Committee lists this taxon as Galapagos/Hawaiian Petrel. Many West Coast experts (and others) consider the documented Pacific Coast birds to be Hawaiian Petrels.
Hawaiian Petrel is endemic to the larger of the Hawaiian Islands. "Hawaiian Petrel is longer-bodied, heavier, and has shorter, but wider wings, shorter, but deeper bill, and entirely white forehead, while Galapagos usually has a dark speckled forehead, although a few are all white", Albatrosses, Petrels & Shearwaters of the World, Onley and Scofield.
The two species together are sometimes called Dark-rumped Petrel (Pterodroma phaeopygia). The taxon, Hawaiian Petrel, has an estimated population of only 400-600 pairs of breeding birds. The largest breeding population is found at Haleakala Crater, Maui, Hawaii, and until recently "is still raided by mongooses, cats and rats, causing a 70 percent breeding failure." Intensive trapping of these predators has recently improved the breeding survival rates (Handbook of the Birds of the World, Volume 1).
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