Ashy Storm-petrel
Encyclopedia
The Ashy Storm Petrel is a small, scarce seabird
of the storm-petrel
family Hydrobatidae. It breeds colonially on islands off the coasts of California
and Mexico
, and is one of six species of storm petrel that live and feed in the rich California Current
system.
in 1864. Both its common and scientific name, homochroa, "uniformly colored", from Ancient Greek
(h)omoia (όμοια), "alike" + "chroma" (χρώμα) "color",
come from its colouration, one authority has suggested naming it Coues's Storm Petrel after its describer.
It is a gregarious bird at sea, feeding nocturnally on cephalopod
s, fish
(particularly the deep sea myctophids, which rise to the sea's surface at night
) and euphausiid krill
such as Thysanoessa spinifera (which also swarm at the surface). They will also attend fishing vessels for the fish oils released when the nets are pulled.
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
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 been recorded living at least 31 years.
, but also northwestern Mexico
. Half the world's population nests on the Farallon Islands
, off San Francisco, other breeding islands include the 8 Channel Islands of California
(San Miguel Island
, Santa Cruz Island
, Anacapa Island
, Santa Barbara Island
, Santa Catalina Island
and San Clemente Island
), and a small population on Mexico
's Coronados
. Outside of the breeding season it is believed to be more widely distributed, foraging on the California Current
, but undertakes no large migration
and doesn't range as far as other species of storm-petrel. In the early fall large flocks can be seen in Monterey Bay
. The birds do not range inland by any significant measure except when storm-blown; for example a record for San Mateo County, California
was considered "unusual" by an experienced naturalist
.
The world population is estimated to be around 10,000 birds, 8,000 of them breeders, 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
and Burrowing Owl
predation, illumination from fishing
boats, introduced predators
such as rats and feral cat
s, and pollution
. Most of the islands that it breeds on are covered by some degree of protection.
Global warming
and climate change
could have a profound impact on the Ashy-Storm petrel. Future changes to coastal California waters due to global warming
could result in warmer, less productive waters, which would mean there would be less food available for the petrels. In addition, ocean acidification
may result in a decline of crustacean
prey species due to the effects that excess CO2 will have on the animals’ shells. Sea-level rise will also threaten certain nesting sites that are located too close to the water.
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...
of the storm-petrel
Storm-petrel
Storm petrels are seabirds in the family Hydrobatidae, part of the order Procellariiformes. These smallest of seabirds feed on planktonic crustaceans and small fish picked from the surface, typically while hovering. The flight is fluttering and sometimes bat-like.Storm petrels have a cosmopolitan...
family Hydrobatidae. It breeds colonially on islands off the coasts of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, and is one of six species of storm petrel that live and feed in the rich California Current
California Current
The California Current is a Pacific Ocean current that moves south along the western coast of North America, beginning off southern British Columbia, and ending off southern Baja California. There are five major coastal currents affiliated with upwelling zones...
system.
Taxonomy
The Ashy Storm Petrel was first described by American ornithologist Elliott CouesElliott Coues
Elliott Coues was an American army surgeon, historian, ornithologist and author.Coues was born in Portsmouth, New Hampshire. He graduated at Columbian University, Washington, D.C., in 1861, and at the Medical school of that institution in 1863...
in 1864. Both its common and scientific name, homochroa, "uniformly colored", from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
(h)omoia (όμοια), "alike" + "chroma" (χρώμα) "color",
come from its colouration, one authority has suggested naming it Coues's Storm Petrel after its describer.
Description and ecology
This is a small, uniformly sooty-brown storm petrel with a forked tail, closely resembling the Black Storm Petrel, however 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
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, fish
Fish
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...
(particularly the deep sea myctophids, which rise to the sea's surface at night
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....
) and euphausiid krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
such as Thysanoessa spinifera (which also swarm at the surface). They will also attend fishing vessels for the fish oils released when the nets are pulled.
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
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...
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
Bird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
individual has been recorded living at least 31 years.
Distribution, Status, and Threats
Ashy Storm Petrel breeds on 17 islands in the northeast Pacific, principally off CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, but also northwestern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Half the world's population nests on the Farallon Islands
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, USA. They lie outside the Golden Gate and south of Point Reyes, and are visible from the mainland on clear days...
, off San Francisco, other breeding islands include the 8 Channel Islands of California
Channel Islands of California
The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...
(San Miguel Island
San Miguel Island
San Miguel Island is the westernmost of California's Channel Islands, located across the Santa Barbara Channel in the Pacific Ocean, within Santa Barbara County, California. San Miguel is the sixth-largest of the eight Channel Islands at , including offshore islands and rocks. Prince Island, off...
, Santa Cruz Island
Santa Cruz Island
Santa Cruz Island was the largest privately owned island off the continental United States, but is currently part-owned by the National Park service . The island, located off the coast of California, is long and from wide...
, Anacapa Island
Anacapa Island
Anacapa Island is a small volcanic island located about off the coast of Port Hueneme, California, in Ventura County. The Island is composed of a series of narrow islets six miles long, running in a mostly east-west orientation, five miles east of Santa Cruz Island...
, Santa Barbara Island
Santa Barbara Island
Santa Barbara Island is a small island of the Channel Islands archipelago in California. It is located about off the Southern California coast from the Palos Verdes Peninsula, near Los Angeles in Ventura County, California....
, Santa Catalina Island
Santa Catalina Island, California
Santa Catalina Island, often called Catalina Island, or just Catalina, is a rocky island off the coast of the U.S. state of California. The island is long and across at its greatest width. The island is located about south-southwest of Los Angeles, California. The highest point on the island is...
and San Clemente Island
San Clemente Island
San Clemente Island is the southernmost of the Channel Islands of California. It is owned and operated by the United States Navy, and is a part of Los Angeles County. Defined by the United States Census Bureau as Block Group 2 of Census Tract 5991 of Los Angeles County, California, it is long and...
), and a small population on Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
's Coronados
Coronado Islands
The Coronado Islands are a group of four islands off the northwest coast of the Mexican state of Baja California. Battered by the wind and waves, they are largely infertile and uninhabited except for a small military detachment and a few lighthouse keepers...
. Outside of the breeding season it is believed to be more widely distributed, foraging on the California Current
California Current
The California Current is a Pacific Ocean current that moves south along the western coast of North America, beginning off southern British Columbia, and ending off southern Baja California. There are five major coastal currents affiliated with upwelling zones...
, but undertakes no large migration
Bird 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...
and doesn't range as far as other species of storm-petrel. In the early fall large flocks can be seen in Monterey Bay
Monterey Bay
Monterey Bay is a bay of the Pacific Ocean, along the central coast of California. The bay is south of San Francisco and San Jose, between the cities of Santa Cruz and Monterey....
. The birds do not range inland by any significant measure except when storm-blown; for example a record for San Mateo County, California
San Mateo County, California
San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and...
was considered "unusual" by an experienced naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
.
The world population is estimated to be around 10,000 birds, 8,000 of them breeders, 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
Western Gull
The Western Gull, Larus occidentalis, is a large white-headed gull that lives on the western coast of North America. It was previously considered conspecific, the same species, with the Yellow-footed Gull of the Gulf of California...
and Burrowing Owl
Burrowing Owl
The Burrowing Owl is a tiny but long-legged owl found throughout open landscapes of North and South America. Burrowing Owls can be found in grasslands, rangelands, agricultural areas, deserts, or any other open dry area with low vegetation. They nest and roost in burrows, such as those excavated...
predation, illumination from fishing
Fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
boats, introduced predators
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...
such as rats and feral cat
Feral cat
A feral cat is a descendant of a domesticated cat that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.In many parts of...
s, and pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
. Most of the islands that it breeds on are covered by some degree of protection.
Global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
and climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
could have a profound impact on the Ashy-Storm petrel. Future changes to coastal California waters due to global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
could result in warmer, less productive waters, which would mean there would be less food available for the petrels. In addition, ocean acidification
Ocean acidification
Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....
may result in a decline of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
prey species due to the effects that excess CO2 will have on the animals’ shells. Sea-level rise will also threaten certain nesting sites that are located too close to the water.