Overview
Ashy storm-petrels are mostly dark grey, medium-sized birds with forked tails and proportionally larger wings. They spend a large portion of their lives at sea, generally only returning to land to breed. They breed on small islands and on coastal rocks on the mainland.
Ashy storm-petrels are found throughout the California Current System with breeding occurring along the coast. The largest breeding concentration is at the South Farallon Islands in central California, but four other concentrations occur in southern California at the Channel Islands.
In 2002, the ashy storm-petrel was designated by the U.S. Fish and Wildlife Service as a Bird of Conservation Concern and is currently designated as such in Marine Bird Conservation Region 17 and Bird Conservation Region 32. A 2007 petition to list ashy storm-petrels as threatened or endangered under the Endangered Species Act of 1973 was sent to the Secretary of the Interior and U.S. Fish and Wildlife Service. The California Department of Fish and Wildlife listed ashy storm-petrels as a Species of Special Concern in 2008. Following status reviews in 2009 and 2012, listing was determined to be not warranted. It is listed as in danger of extinction at the federal level in Mexico. In 2018, the ashy storm-petrel was listed as endangered by the International Union for Conservation of Nature.
Updated estimates describing the abundance and distribution of ashy storm-petrels from the last century are lacking. This is largely in part due to their at-sea lifestyle, where they are difficult to monitor and study, as well as secretive burrow nesting behavior of this species. However, detailed reports and observations make it evident that there has been a decrease in their populations. Even so, most conservation concerns have been identified primarily in a few key areas where ashy storm-petrel observation and research is easier. Introduction and increased presence of avian and mammalian predators have largely contributed to the decline in ashy storm-petrels at breeding colony locations. Habitat loss due to coastal development and climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change is a major stressor due to the birds' reliance on offshore and coastal rocky areas for breeding. Historically, pollution has been a threat for seabirds and although some concerns are fading, others are still not well understood. As the world seeks to find answers for clean sources of energy, offshore wind projects are a promising lead, however wind turbines placed offshore may have adverse effects to ashy storm-petrels.
Scientific Name
Identification Numbers
Characteristics
Physical Characteristics
Ashy storm-petrels calls are raspy squawks that go from a high to low pitch. They can be used as single calls or rapidly in succession.
The average weight of ashy storm-petrels is 1.3 ounces (36.9 grams).
Overall dark grey in plumage with pale bands on the upper tail and wing. Primaries and secondaries are darker than the rest of the body. Males and females are similar in appearance regardless of age.
Ashy storm-petrels are medium sized birds with proportionally larger wings and a forked tail.
Measurements:
Body Length: 8 in (20.32 cm)
Wingspan: 18 in (45.72 cm)
Food
Ashy storm-petrels feed almost entirely at night on small fish, squid and surface-dwelling crustaceans. They are known to follow fishing vessels and scavenge for bycatch and fish oils. Ashy storm-petrels have been found to consume small plastic particles while out at sea, but little is understood about its effect on them. Like most seabirds, they drink sea water excreting the salt through their supraorbital glands.
Life Cycle
Ashy storm-petrels are known to live up to 30 years, but data on longevity of the species is limited.
Ashy storm-petrels do not migrate and spend most of their lives at sea, generally only coming to land to breed. They may begin visiting land-based breeding colonies in December. Timing of breeding can be variable and colony members do not all breed at the same time. Nesting and egg laying can range from as early as April and as late as September. First chick fledging begins in June and may last into January.
Ashy storm-petrels spend a large portion of their lives at sea, generally only coming to land during the breeding season with occasional visits to breeding areas throughout the rest of the year. As the breeding season approaches, birds begin to arrive at breeding colonies in December. They breed on small offshore islands and on coastal rocks on the mainland. Rock crevices, rocky slopes, rock walls and caves are especially appealing.
Ashy storm-petrels breeding pairs are monogamous. Their pre-egg period is longer than most sea birds, with courtship and preparation of nesting sites lasting for months at a time. Nesting sites are within natural or artificial cavities with no excavation done by the birds. Ashy storm-petrels do not build nests. Occasionally, very limited vegetation may be added to the cavities. Cavities may be shared with other pairs, including those of other species of cavity nesting seabirds.
Egg laying can begin as early as April and end as late as September; however, the majority of eggs are laid between June and July. Females lay one egg per year with replacement eggs being rare. Incubation occurs for 45 days after the egg is laid with parents alternating incubation every one to eight days. Before the incubation period begins, the pair will lose the downy feathers on their bellies to facilitate the incubation process.
Chicks are altricial, meaning that they are underdeveloped at birth, and are fed every one to three nights. Fledging of the chicks occurs at night after an average of 84 days after hatching. Fledging of chicks can occur as early as June and as late as January. Once the young fledge and leave the nests, they are independent of their parents.
Similar Species
Including the ashy storm-petrel, there are six species of storm-petrels that occupy the California Current System. Of these, Wilson's storm-petrel, Leach's storm-petrel, black storm-petrel and least storm-petrel are most similar in appearance to ashy storm-petrels. Because differentiating size and color at sea can be difficult, ashy storm-petrels can best be discerned through their faster and shallower wingbeats.
Behavior
During the non-breeding season, ashy storm-petrels live at sea. Feeding at night, they hover and skim low over water to forage with relatively fast wingbeats. They sit on the water to feed. Little is known about their at-sea behavior due to limited research. Ashy storm-petrels return to land to breed in colonies and feed almost exclusively at night.
Habitat
Ashy storm-petrels spend most of their lives at sea and generally only return to land to breed. With few exceptions, they will typically avoid neritic waters and stay in the oceanic zone. However, ashy storm-petrels breed on small islands and on mainland coastal rocks. It is in these areas where rock crevices, rocky slopes, rock walls and caves are most attractive to these birds. Due to rapid development in the last century, ashy storm-petrels have taken advantage of natural and man-made areas such as developed coastal areas and artificial habitats.
Of or relating to the sea.
The land near a shore.
Geography
During the non-breeding season, ashy storm-petrels spend most of their time out at sea. Due to this, their at-sea distribution is not well understood or documented, however they are found throughout the California Current System.
Breeding sites are located along the coast of California all the way to Baja California. There are 33 locations confirmed to hold breeding ashy storm-petrels. The largest breeding concentration is on the South Farallon Islands in central California, but four other breeding concentrations occur in southern California on the Channel Islands, on or adjacent to San Miguel and Santa Barbara islands, and on northwest and northeast Santa Cruz Island.
Timeline
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