Bonin Petrel
Encyclopedia
The Bonin Petrel, Pterodroma hypoleuca, is a seabird
in the family
Procellariidae
. It is a small gadfly petrel
that lives in the waters of the north west Pacific and nests on islands south of Japan
and in the Northwestern Hawaiian Islands
. Its secretive habits and limited range have resulted in few studies and many aspects of the species biology
are poorly known.
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.
The Bonin Petrel is currently thought to be closely related to the Mottled Petrel
and White-necked Petrel
in the subgenus Proaestrelata, based on a review of the whole Pterodroma genus looking at morphology, calls, breeding biology, diet and parasitic lice. Despite the species having two remote and separate breeding localities the species is monotypic and no subspecies are recognised.
dominated diet. Principal prey items are fish from the family Myctophidae (lantern fish) and Sternoptychidae
(hatchetfish). Squid
from the family Ommastrephidae
are also consumed. All of these prey are midwater residents that use photophore
s and migrate to the surface during the night to feed; thus it is assumed that Bonin Petrels are 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.
, Laysan
, Lisianski Island
, Pearl and Hermes Reef, Midway Atoll
and Kure Atoll
; and on the Volcano Islands
and Bonin Islands south of Japan. 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, and are between 1-3m long. Pairs are territorial, and will defend an area of around 2m around the burrow entrance. They also display philopatry
, returning to the same burrow in consecutive years, redigging the burrow if it has collapsed.
The species is thought to mate for life (like other Procellariiformes
); pairs undertake mating flights consisting of pairs chasing and calling at each other over the colony prior to laying. A single egg is laid by a pair per breeding season, if it is lost then no attempt is made to relay. Laying occurs in late January. Both parents incubate the egg, with incubation stints of eight days for the male and six days for the female. Hatching occurs after around 50 days, around mid-March. The chicks are semi-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.
northwards to the seas off Honshū
and Sanriku
in Japan. The timing of the migration is partly influenced by sea surface temperature
s. 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.
, fossil
remains have been found on Kauai
, Oahu
and Molokai
. These bones have been found in association with human archeology, 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. Polynesian rat
s and black rat
s 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. 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. Island restoration
projects are restoring native vegetation on Laysan and Midway, and rats and rabbits have been removed from all the Northwestern Hawaiian Islands. The species is currently classified as 'least concern'.
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Procellariidae
Procellariidae
The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes , which also includes the albatrosses, the storm-petrels, and the diving petrels.The procellariids are...
. It is a small gadfly petrel
Gadfly petrel
The gadfly petrels are seabirds in the bird order Procellariiformes. These medium to large petrels feed on food items picked from the ocean surface....
that lives in the waters of the north west Pacific and nests on islands south of Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and in the Northwestern Hawaiian Islands
Northwestern Hawaiian Islands
The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...
. Its secretive habits and limited range have resulted in few studies and many aspects of the species biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
are poorly known.
Description and taxonomy
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 a 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 plumagePlumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
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.
The Bonin Petrel is currently thought to be closely related to the Mottled Petrel
Mottled Petrel
The Mottled Petrel is a species of seabird and a member of the gadfly petrels. The bird is 33-35 cm in size, with a 74-82 cm wingspan....
and White-necked Petrel
White-necked Petrel
The White-necked Petrel , also known as the White-naped Petrel, is a species of seabird in the Procellariidae family. During non-breeding season it occurs throughout a large part of the Pacific, but it is only known to breed on Macauley Island in New Zealand's Kermadec Islands and the Australian...
in the subgenus Proaestrelata, based on a review of the whole Pterodroma genus looking at morphology, calls, breeding biology, diet and parasitic lice. Despite the species having two remote and separate breeding localities the species is monotypic and no subspecies are recognised.
Diet
The Bonin Petrel and the closely related Mottled Petrel are the only Pterodroma petrels with a fishFish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
dominated diet. Principal prey items are fish from the family Myctophidae (lantern fish) and Sternoptychidae
Sternoptychidae
The marine hatchetfishes or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform family Sternoptychidae...
(hatchetfish). Squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
from the family Ommastrephidae
Ommastrephidae
Ommastrephidae is a family of squid. It contains 3 subfamilies, 11 genera, and over 20 species.-External links:***...
are also consumed. All of these prey are midwater residents that use photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s and migrate to the surface during the night to feed; thus it is assumed that Bonin Petrels are nocturnal feeders
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....
that seize prey at the surface while resting on the sea or in flight. Bonin Petrel eyes contain high levels of the pigment rhodopsin
Rhodopsin
Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...
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
Stomach oil
Stomach oil is the light oil composed of neutral dietary lipids found in the proventriculus of birds in the order Procellariiformes. All albatrosses, procellarids and storm-petrels use the oil...
, an energy rich oil which is lighter to carry than prey.
Breeding
The Bonin Petrel breeds in dense colonies, on islands in the Northwestern Hawaiian Islands; French Frigate ShoalsFrench Frigate Shoals
The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals...
, Laysan
Laysan
Laysan , located northwest of Honolulu at N25° 42' 14" W171° 44' 04", is one of the Northwestern Hawaiian Islands. It comprises one land mass of , about 1 by 1.5 miles in size . It is an atoll of sorts, although the land completely surrounds a shallow central lake some above sea level that has...
, Lisianski Island
Lisianski Island
Lisianski Island is one of the Northwestern Hawaiian Islands, with a land area of and a maximum elevation of above sea level. Honolulu is away, to the southeast. Linked to Lisianski are the extensive Neva Shoals...
, Pearl and Hermes Reef, Midway Atoll
Midway Atoll
Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...
and Kure Atoll
Kure Atoll
Kure Atoll or Ocean Island is an atoll in the Pacific Ocean beyond Midway Atoll in the Northwestern Hawaiian Islands at . The only land of significant size is called Green Island and is habitat for hundreds of thousands of seabirds...
; and on the Volcano Islands
Volcano Islands
The Volcano Islands is a group of three Japanese islands south of the Bonin Islands that belong to the municipality of Ogasawara...
and Bonin Islands south of Japan. 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
Wedge-tailed Shearwater
The Wedge-tailed Shearwater, Puffinus pacificus is a medium-large shearwater in the seabird family Procellariidae. It is one of the shearwater species that is sometimes referred to as a Muttonbird, like the Sooty Shearwater of New Zealand and the Short-tailed Shearwater of Australia...
, 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, and are between 1-3m long. Pairs are territorial, and will defend an area of around 2m around the burrow entrance. They also display philopatry
Philopatry
Broadly, philopatry is the behaviour of remaining in, or returning to, an individual's birthplace. More specifically, in ecology philopatry is the behaviour of elder offspring sharing the parental burden in the upbringing of their siblings, a classic example of kin selection...
, returning to the same burrow in consecutive years, redigging the burrow if it has collapsed.
Procellariiformes
Procellariiformes is an order of seabirds that comprises four families: the albatrosses, petrels and shearwaters, storm petrels, and diving petrels...
); pairs undertake mating flights consisting of pairs chasing and calling at each other over the colony prior to laying. A single egg is laid by a pair per breeding season, if it is lost then no attempt is made to relay. Laying occurs in late January. Both parents incubate the egg, with incubation stints of eight days for the male and six days for the female. Hatching occurs after around 50 days, around mid-March. The chicks are semi-altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
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
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
around 80 days after hatching, in early June.
Migration
After the breeding season both chicks and adults migrateBird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
northwards to the seas off Honshū
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...
and Sanriku
Sanriku
is a historical region of Japan on the northeastern side of the island of Honshu, corresponding to today's Aomori, Iwate and parts of Miyagi Prefecture...
in Japan. The timing of the migration is partly influenced by sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s. 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 IslandsHawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
, fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains have been found on Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
, Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
and Molokai
Molokai
Molokai or Molokai is an island in the Hawaiian archipelago. It is 38 by 10 miles in size with a land area of , making it the fifth largest of the main Hawaiian Islands and the 27th largest island in the United States. It lies east of Oahu across the 25-mile wide Kaiwi Channel and north of...
. These bones have been found in association with human archeology, strongly implying that they were a food source for Polynesian
Polynesians
The Polynesian peoples is a grouping of various ethnic groups that speak Polynesian languages, a branch of the Oceanic languages within the Austronesian languages, and inhabit Polynesia. They number approximately 1,500,000 people...
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
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
, particularly rats. Polynesian rat
Polynesian Rat
The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...
s and black rat
Black Rat
The black rat is a common long-tailed rodent of the genus Rattus in the subfamily Murinae . The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world.-Taxonomy:The black rat was...
s 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
Laysan Rail
The Laysan Rail or Laysan Crake was a tiny inhabitant of the Northwest Hawaiian Island of Laysan. This small island was and still is an important seabird colony, and sustained a number of endemic species, including the rail. It became extinct due to habitat loss by domestic rabbits, and ultimately...
) reduced the population of Bonin Petrels from 500,000 birds to 32,000 by 1995. 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. Island restoration
Island restoration
The ecological restoration of islands, or island restoration, is the application of the principles of ecological restoration to islands and island groups. Islands, due to their isolation, are home to many of the world's endemic species, as well as important breeding grounds for seabirds and some...
projects are restoring native vegetation on Laysan and Midway, and rats and rabbits have been removed from all the Northwestern Hawaiian Islands. The species is currently classified as 'least concern'.