The Hawaiian petrel or 'Ua'u (Pterodroma sandwichensis) is a large, dark grey-brown and white petrel, formerly found on all the main Hawaiian Islands except Niihau. Their feet are bicolored pink and black. The 'Ua'u is now mostly restricted to Haleakala crater on Maui with smaller numbers on Mauna Loa on the island of Hawaii, Waimea Canyon on the island of Kauai, Lanai, and possibly Molokai. Their diet consists of 50-75% squid, and smaller percentages of fish and crustaceans. The birds nest in burrows or rock crevices. The breeding extends from March to October. The female lays one white egg. When the chick hatches, the parents go out to sea and feed during the day, and return only at night. They pass their food on to the chicks by means of regurgitation. The chicks are charcoal-gray colored and were considered a delicacy by early Hawaiians. Scientists previously thought that the petrels remained relatively close to shore during the breeding season. New research employing microwave telemetry shows that the birds travel as far as Alaska and Japan during two week-long feeding trips. When returning to nest burrows at night, adults make a distinctive moaning "oo-ah-oo." At their burrows, adult birds also make a variety of yaps, barks, and squeals. The petrel's flight is characterized by high, steeply banked arcs and glides. Their wings are long and narrow with a wingspan of 36 inches. The wings and tail are sooty-colored. The Hawaiian Petrel is an endangered species. The greatest threats to the petrel are feral cats, mongooses, and rats, all of which feed on the helpless chicks when they are inside their burrows. In Haleakala National Park, great efforts are being made to reduce the number of feral animals, so to preserve not only the Hawaiian Petrel, but many other rare Hawaiian birds that fall victim to predation. The Hawaiian Petrel was once considered conspecific with the Dark-rumped Petrel of the Galápagos islands, but was recently split to its own species.