Bonin petrel

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Bonin petrel
On Midway Atoll

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Procellariiformes
Family: Procellariidae
Genus: Pterodroma
Species:
P. hypoleuca
Binomial name
Pterodroma hypoleuca
(Salvin, 1888)

The Bonin petrel or nunulu[2] (Pterodroma hypoleuca) is a seabird in the family Procellariidae. It is a small gadfly petrel that is found in the northwest Pacific Ocean. Its secretive habits, remote breeding colonies and limited range have resulted in few studies and many aspects of the species' biology are poorly known.

Taxonomy

The Bonin petrel was

Pterodroma that was introduced by French naturalist Charles Lucien Bonaparte in 1856.[5][6] The genus name combines the Ancient Greek
pteron meaning "wing" with dromos meaning "racer" or "runner". The specific epithet hypoleuca is from the Ancient Greek hupi meaning "beneath" with leukos meaning "white". [7] Despite the species having two remote and separate breeding localities the species is monotypic and no subspecies are recognised.[6]

The Bonin petrel is currently thought to be closely related to the

lice.[8]

Description

The Bonin petrel is a small gadfly petrel, 30 cm long with a wingspan of around 67 cm. It has a white head with a black cap and face markings; overall the head often has a scaled appearance. Its pale grey upperparts have darker primaries and wing coverts creating an "M" mark across the back. The underwing is white with dark edging and a patch at the carpal joint and across underwing coverts. The tail is dark grey, and the rest of the plumage is white, except for a dark half collar on the breast. Like the rest of the Pterodroma petrels the black bill is short and hooked. The legs and feet are pink with dark patches.

Distribution and population

Despite the species's name, 995,000 individuals, about 99% of the total population, breed on the

Ogasawara and Volcano Islands
.

Behaviour

Diet

The Bonin petrel and the closely related mottled petrel are the only Pterodroma petrels with a

nocturnal feeders that seize prey at the surface while resting on the sea or in flight. Bonin petrel eyes contain high levels of the pigment rhodopsin which aids nocturnal vision. The Bonin petrel is usually solitary at sea, but is occasionally seen in large multi-species flocks. Like all procellariids the Bonin petrel has a modified area of the gut known as a proventriculus which partly digests prey to create stomach oil
, an energy rich oil which is lighter to carry than prey.

Breeding

A Bonin petrel trapped in the sand on Midway Atoll by the 2011 Tōhoku earthquake and tsunami, before being rescued.

The Bonin petrel breeds in dense

Pearl and Hermes Reef, Midway Atoll and Kure Atoll; and on the Volcano Islands and Bonin Islands south of Japan. Colonies are only visited by birds at night, with birds usually arriving soon after sunset.[10] Nesting occurs in the winter in order to avoid competition for burrows with other nesting procellariids. In the Northwestern Hawaiian Islands the nesting season sometimes overlaps with the larger wedge-tailed shearwater, which will evict and even kill Bonin petrel chicks in order to use the nesting burrows. Both parents participate in digging burrows, which are usually dug in sand or hard coral substrate, and are between 1 and 3 m long. Pairs are territorial, and will defend an area of around 2 m around the burrow entrance. They also display philopatry, returning to the same burrow in consecutive years, redigging the burrow if it has collapsed. Burrows in harder coral substrate are less likely to collapse than those dug into sand.[10]

Bonin petrel chick

The species is thought to mate for life (like other

altricial at hatching, covered in light grey down, and are brooded by the adults for two days after hatching, after which both parents feed at sea and return at night to feed the chick. Chicks are fed stomach oil and small items of prey. Chicks fledge
around 80 days after hatching, in early June.

Migration

After the breeding season both chicks and adults

Honshū and Sanriku in Japan. The timing of the migration is partly influenced by sea surface temperatures
. Birds begin to disperse south and east again in August and begin to return to their breeding islands in September. During the breeding season birds feed in the waters surrounding breeding islands. The species has not been recorded in the east Pacific.

Relationship with humans

Prior to the arrival of humans the Bonin petrel nested on the main Hawaiian Islands, fossil remains have been found on Kauai, Oahu and Molokai. These bones have been found in association with human archaeology, strongly implying that they were a food source for Polynesian settlers, along with other seabirds. The species was extirpated from the main islands prior to the arrival of Europeans.

The species is currently threatened by introduced species, particularly rats.[11] Polynesian rats and black rats have devastated populations of Bonin petrels in the Northwestern Hawaiian Islands, primarily by taking eggs. Polynesian rats introduced to Kure Atoll were such a problem for Bonin petrels that for a five-year period in the 1960s not a single chick fledged (hatching success can be as high as 90% in the absence of introduced predators). Similar devastation occurred on Midway, where black rats introduced in 1943 (the same black rats that caused the extinction of the Laysan rail) reduced the population of Bonin petrels from 500,000 birds to 32,000 by 1995.[12] Rabbits introduced to Lisianski Island destroyed nesting habitat and undermined nesting burrows. Habitat destruction limits breeding success on some islands, especially as it increases competition with more aggressive species like the wedge-tailed shearwater.

Conservation measures are in place to protect the Bonin petrel and other seabirds that share the species' breeding islands.

IUCN.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2018-2.RLTS.T22697967A132615616.en
    . Retrieved 12 November 2021.
  2. ^ Gregg, Jason (12 May 2021). "Decolonizing Seabirds". Hakai Magazine. Archived from the original on 2021-05-12. Retrieved 2021-05-14.
  3. ^ Salvin, Osbert (1888). "Critical notes on the Procellariidae". Ibis. 5th Series. 6: 351–360 [359].
  4. ^ Mayr, Ernst; Cottrell, G. William, eds. (1979). Check-List of Birds of the World. Vol. 1 (2nd ed.). Cambridge, Massachusetts: Museum of Comparative Zoology. p. 76.
  5. ^ Bonaparte, Charles Lucien (1856). "Espèces nouvelles d'oiseaux d'Asie et d'Amérique, et tableaux paralléliques des Pélagiens ou Gaviae". Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences (in French). 42: 764–776 [768].
  6. ^
    Rasmussen, Pamela, eds. (July 2021). "Petrels, albatrosses"
    . IOC World Bird List Version 11.2. International Ornithologists' Union. Retrieved 4 January 2022.
  7. ISBN 978-1-4081-2501-4
    .
  8. doi:10.1111/j.1474-919X.1985.tb05055.x
    .
  9. ^ Harrison, C. S., T. S. Hida, M. P. Seki. (1983). "Hawaiian seabird feeding ecology". Wildl. Monogr. 85: 171.
  10. ^ a b Grant, Gilbert; Warham, John; Pettit, Ted; Whittow, Causey (1983). "Reproductive Behavior and Vocalizations of the Bonin Petrel" (PDF). The Wilson Journal. 95 (4): 522–539.
  11. JSTOR 1521854
    .
  12. ^ Seto, N. W. H., and D. O’Daniel. 1999. Bonin Petrel (Pterodroma hypoleuca). In The Birds of North America, No. 385 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
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