Haleakala Crater, breeding grounds for the dark-rumped petrel
PHOTO BY FRANK RICHARDSON
Dark-rumped petrel
DARK-RUMPED PETREL Pterodroma phaeopygia
(Hawaiian name—uau)
DESCRIPTION: 15″. Underparts, forehead, and cheeks, white; back, upper wings, and upper tail, dark. The crown is black.
PARK DISTRIBUTION: This petrel is a sea bird that nests in the mountains of the Hawaiian group; it is the nesting birds that may be seen or heard within the park between May and November. Kilauea—Status unknown; the cliffs of Kilauea Crater may be used for nesting. Haleakala—Many birds nest in the walls of the crater. The cliffs behind Kapalaoa and Holua Cabins are the best places to hear them at night.
VOICE: As the birds fly overhead seeking their burrows after dusk, the air is filled with their strange calls, some of which sound like the barking of a small dog. A common pattern of notes is oooo-wéh, ooo-wéh, oo-wéh, oo-wéh, etc., with the first notes drawn out and the last run together in rapid succession.
Dark-rumped Petrels spend most of their life at sea, but in April and May they begin their nightly flights inland to burrows they have established high on the cliffs of Hawaiian volcanoes. A single egg is laid near the end of the horizontal cavity that may be more than 6 feet deep in the rocks. For the next 6 months the adults will fly in from the ocean each night to tend the nest, arriving about an hour after sundown. It is while they are circling in search of the burrows that you can hear their mysterious barking sounds. The calling may continue for 2 hours or more. Imagine the problems that each petrel must face trying to find its own burrow 20 miles from the ocean on a foggy, moonless night—perhaps the continuous calling back and forth helps orient it. The adults return to the ocean before sunrise.
In the early days nesting birds were common on all the main Hawaiian Islands; however, for a time it was feared that they were becoming extinct. Hawaiians used to dig out the downy young petrels for food, and introduced mongooses and cats also took a heavy toll, especially where nests were at lower elevations. Now, with known breeding colonies high on Haleakala and Mauna Kea and probably on Mauna Loa and Kilauea, the future of this interesting species seems assured.