The ashy storm petrel (''Hydrobates homochroa'') is a small, scarce

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

of the

storm petrel Storm petrel or stormy petrel may refer to one of two bird family (biology), families, both in the order Procellariiformes, once treated as the same family. The two families are: * Northern storm petrels (''Hydrobatidae'') are found in the No ...

family

Hydrobatidae Northern storm petrels are seabirds in the genus ''Hydrobates'' in the Family (biology), family Hydrobatidae, part of the order Procellariiformes. The family was once Lumpers and splitters, lumped with the similar austral storm petrels in the co ...

. It breeds colonially on islands off the coasts of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, and is one of six species of storm petrel that live and feed in the rich

California Current The California Current () is a cold water Pacific Ocean ocean current, current that moves southward along the western coast of North America, beginning off southern British Columbia and ending off southern Baja California Sur. It is considered an ...

system.

Taxonomy

The ashy storm petrel was first described by American ornithologist

Elliott Coues Elliott Ladd Coues (; September 9, 1842 – December 25, 1899) was an American army surgeon, historian, ornithologist, and author. He led surveys of the Arizona Territory, and later as secretary of the United States Geological and Geographi ...

in 1864. Both its common and scientific name, ''homochroa'', "uniformly colored", from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

(h)omoia (''όμοια''), "alike" + "chroma" (''χρώμα'') "color", come from its coloration. It was formerly defined in the genus '' Oceanodroma'' before that genus was synonymized with '' Hydrobates''.

Description and ecology

This is a small, uniformly sooty-brown storm petrel with a forked tail, closely resembling the black storm petrel, but it is smaller and has a more fluttering style of flight, with the upstroke only becoming horizontal to the body before beginning the downstroke (other storm petrels in its range have a higher upstroke). It is a gregarious bird at sea, feeding nocturnally on

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

(particularly the deep-sea myctophids, which rise to the sea's surface at night) and euphausiid

krill Krill ''(Euphausiids)'' (: krill) are small and exclusively marine crustaceans of the order (biology), order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian language, Norwegian word ', meaning "small ...

such as '' Thysanoessa spinifera'', which also swarm at the surface. They also attend fishing vessels for the fish oils released when the nets are pulled. Oceanodroma homochroa MHNT ZOO 2010 11 42 California Naurois

Oceanodroma homochroa MHNT ZOO 2010 11 42 California Naurois

Ashy storm petrels nest in rock burrows on offshore islands, returning to the nests at night. The species has a long breeding cycle, laying eggs in May and

fledging Fledging is the stage in a flying animal's life between hatching or birth and becoming capable of flight. This term is most frequently applied to birds, but is also used for bats. For altricial birds, those that spend more time in vulnerable c ...

in October, although timing varies greatly, more so than in most other storm petrels; some pairs may have a chick that is half grown when other pairs are still laying. Like in many other seabirds, pairs show both mate and site fidelity, mating in the same pair with the same mate for many years and nesting at the same burrow, despite the pairs spending their lives out of the breeding season separate from each other, and despite the fact that many individuals might seem to compete for burrows at the nesting colonies. A change in mate is usually associated with a change in nesting site. The ashy storm petrel is a long-lived bird; a banded individual has lived at least 31 years.

Distribution, status, and threats

Ashy storm petrels breed on 17 islands in the northeast

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

, principally off the coast of

, but including a few sites off the coast of northwestern

. Half the world's population nests on the

Farallon Islands The Farallon Islands ( ), or Farallones (), are a group of islands and sea stacks in the Gulf of the Farallones, off the coast of San Francisco, California, United States. The islands are also sometimes referred to by mariners as the Devil's ...

near

San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

. Other breeding islands include the eight

Channel Islands of California The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. They define the Santa Barbara Channel between the islands and the California mainland. The ...

and a small population on Mexico's Coronados. Bat Cave, on the north side of Santa Cruz Island in Southern California, has the largest nesting colony for the ashy storm petrel in the world, with over 100 nests. Outside of the breeding season, it is believed to be more widely distributed, foraging on the

, but it undertakes no large

migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...

and does not range as far as other species of storm petrels. In the early fall, large flocks can be seen in

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area. San Francisco itself is further north along the coast, by about 75 miles (120 km), accessible via California S ...

. The birds do not range inland any significant distance except when storm-blown; for example, a sighting in

San Mateo County, California San Mateo County ( ), officially the County of San Mateo, is a county (United States), county located in the U.S. state of California. As of the 2020 United States census, the population was 764,442. Redwood City, California, Redwood City is th ...

was considered "unusual" by an experienced

naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

. The world population is estimated to be around 10,000 birds, 8,000 of them breeders, with the Farallon population having declined by one-third between 1972 and 1992. The ashy storm petrel is designated as a species of conservation concern in California. It is threatened by

western gull The western gull (''Larus occidentalis'') is a large white-headed gull that lives on the west coast of North America and the Pacific Ocean. The western gull ranges from British Columbia, Canada, to Baja California, Mexico. It was previously con ...

and

burrowing owl The burrowing owl (''Athene cunicularia''), also called the shoco, is a small, long-legged, primarily terrestrial—though not flightless—species of owl native to the open landscapes of North and South America. They are typically found in gra ...

predation, illumination from fishing boats, introduced predators such as rats and

feral cat A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact; it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...

s, and

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

. Most of the islands where it breeds are covered by some degree of protection.

Global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

could have a profound impact on ashy storm petrels. Future changes to coastal California waters due to global warming could result in warmer, less productive waters, which would mean less food would be available for the petrels. In addition,

ocean acidification Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ...

may result in a decline of

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

prey species due to the effects that excess CO₂ will have on the animals' shells.

Sea-level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

will also threaten certain nesting sites that would be located too close to water.

References

External links

Ashy storm petrel Species Account
– Cornell Lab of Ornithology

- BirdLife International {{Taxonbar, from=Q1269924 ashy storm petrel Birds of Mexico Native birds of the West Coast of the United States Ashy storm petrel Ashy storm petrel Ashy storm petrel Ashy storm petrel Ashy storm petrel ashy storm petrel ashy storm petrel

Taxonomy

Description and ecology

Distribution, status, and threats

References

Further reading

External links