‘Ou – Bulwer’s Petrel
Bulweria bulwerii
| Stated-recognized | Indigenous |
| NatureServe Heritage Rank | G4 – Apparently secure |
| North American Waterbird Conservation Plan |
Moderate concern |
| Regional Seabird Conservation Plan |
USFWS 2005 |
The ‘Ou, or Bulwer’s Petrel, is a highly pelagic, nocturnal gadfly petrel belonging to the family Procellariidae. This bird is typically found in tropical regions. It has long, pointed wings, a long, pointed tail, a black bill, and short, pale legs. Both adult males and females have a sooty brown appearance, with a pale bar across the proximal half of their upper wings. The flight of the ‘Ou is buoyant and erratic, characterized by low flying over the water, using short wing beats followed by glides. The ‘Ou typically forages alone.
Foraging behavior and diet are not well understood. This species likely captures prey at the surface by dipping while in flight or by seizing prey while perched on the water. Its diet consists mainly of fish and squid, but it also includes crustaceans and sea-striders.
Bulwer’s petrel (known as ‘Ou) forms long-term pair bonds and breeds in large colonies. Limited data suggest that these birds return to their natal colonies to breed, and pairs often return to the same nest site year after year. Nests are typically located in various hollows or crevices. They have a noticeable musky odor and can consist of nothing more than a bare cavity floor, although some may be lined with feathers, vegetation, or rubble.
In Hawai‘i, eggs are laid between mid-May and mid-June, with most nestlings fledging by early October. Both parents incubate the eggs, brood, and feed the chicks.
‘Ou (Bulwer’s Petrel) breed throughout the Northwestern Hawaiian Islands (NWHI) and on several offshore islets of the Main Hawaiian Islands (MHI), including Hulu, Kaeoi, Kāohikaipu, Kapapa, Ka‘ula, Lehua, Mānana, Moke‘ehia, Mōkōlea Rock, Moku Lua, Moku Manu, Mokuho‘oniki, Molokini, and Popoi‘a.
Outside of Hawai‘i, the ‘ou breeds on a limited number of islands in the North Atlantic, North and South Pacific, and the Indian Ocean. The range during the non-breeding season is not well understood, but the birds have been observed dispersing to the southeast after breeding.
In Hawai‘i, the estimated population of breeding pairs is between 75,000 and 103,000 on the Northwestern Hawaiian Islands (NWHI) and between 500 and 1,000 pairs on the Main Hawaiian Islands (MHI). The largest colony is located on Nihoa, with an estimated 75,000 to 100,000 pairs, making it the world’s largest known breeding colony of this species. Smaller colonies can be found on Laysan (1,000 to 2,000 pairs), French Frigate Shoals (200 to 500 pairs), and Necker (250 to 500 pairs). Before the introduction of rats (Rattus spp.) to Midway, the ‘ou (Bulwer’s Petrel) population was abundant. The total worldwide population remains unknown.
The following management goals are essential to Pacific seabird conservation: maintain, protect, and enhance habitat; eradicate or control non-natives; minimize bycatch and other adverse effects of fishing; improve the effectiveness of oil spill response efforts; identify contaminants and hazardous substances; and minimize the impact of powerlines, towers, wind turbines, and lights (USFWS 2005). The goal of these management actions is not only to protect seabird populations and their breeding colonies, but also to re-establish former breeding colonies, thereby reducing the risk of extinction.
Introduced Predators: Like all seabirds, adults and their nests are vulnerable to predation by rats (Rattus spp.) and feral cats (Felis silvestris). Fortunately, all sites in the Northwestern Hawaiian Islands (NWHI) are free from both rats and cats.
Invasive Species: On Lisianski and Laysan Islands, rabbits (Oryctolagus cuniculus) have severely reduced suitable nesting locations by denuding the vegetation. Additionally, Golden Crown-beard (Verbesina encelioides) further degrades these crucial nesting habitats. At Kure, introduced Big-headed Ants (Pheidole megacephala) may contribute to nestling mortality and facilitate the destruction of native vegetation by supporting a non-native scale insect.
Bulwer’s Petrel
James Bulwer, a Scottish clergyman and amateur naturalist, collected the type specimen of Bulwer’s Petrel in the Desertas Islands for Sir William Jardine in 1828. Aside from this contribution, he focused on conchology and archaeology, living quietly in Norfolk.
Bulwer’s Petrel, a small and little-known nocturnal seabird, is one of two species in its genus—the other being Jouanin’s Petrel (Bulweria fallax), which is restricted as a breeder to the northwest Indian Ocean.
What’s in a Name?
A webinar related to the research of the Papahānaumokuākea Native Hawaiian Cultural Working Group tasked with giving Hawaiian names to numerous other bird, plant, limu, and coral species unique to PMNM
