Scripps's murrelet

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Scripp's murrelet
ScrippsMurrelet.jpg
Scientific classification
Kingdom Information
Domain Eukaryota
Kingdom Animalia
Subkingdom Bilateria
Branch Deuterostomia
Phylum Information
Phylum Chordata
Sub-phylum Vertebrata
Infraphylum Gnathostomata
Class Information
Superclass Tetrapoda
Class Aves
Sub-class Neornithes
Infra-class Neoaves
Order Information
Superorder Passerimorphae
Order Charadriiformes
Infraorder Charadriides
Family Information
Superfamily Laroidea
Family Alcidae
Sub-family Alcinae
Tribe Information
Tribe Synthliboramphini
Genus Information
Genus Synthliboramphus
Species Information
Species S. scrippsi
Population statistics
Population 30,000 (2012 est.)
Conservation status Vulnerable[1]

Scripp's murrelet (Synthliboramphus scrippsi) is a small seabird of the family Alcidae, and found on the western coast of North America.

Description

Scripp's murrelet is a small, relatively slim alcid, with a body length of 7.9-9.4 inches, a wingspan of 15 inches, and a body weight of up to six ounces. Females are slightly heavier than males. The legs are set very far back on the body, giving it an awkward appearance on land.

The top is completely black. Freshly grown plumage has a slightly bluish luster, while worn plumage looks greyish. The bottom is white, with the white area extending up the throat to the sides of the head. Unlike its close relative, the Guadalupe murrelet, this white area does not encircle the eyes. The small and pointed beak is black. The legs and toes are slightly bluish; the webs are black. Scripp's murrelets have a fast wing beat, and barely ripple the surface of the water when they take flight.

Young birds resemble adult birds, but have faint tufts on the flanks and a slightly shorter beak than adult birds.

Xantus’s murrelet

This bird was once known as Xantus’s murrelet,[2] first described in 1859 by John Xantus de Vesey, a Hungarian naturalist and zoologist who wrote a detailed, if somewhat plagiarized, account of his travels in Baja California. It was there he collected and described many plant and animal species unknown to science at that time, including the murrelet named for him. The bird was recognized as having two subspecies:

  • Synthliboramphus hypoleucus hypoleucus, Guadalupe murrelet
  • Synthliboramphus hypoleucus scrippsi, Scripp's murrelet

In 2012 the American Ornithologists Union formally separated these birds into two distinct species, based on genetic and physical differences, lack of inter-breeding, and separated nesting sites.[3]

Range

This species has one of the southernmost distribution areas among all alcids. Breeding areas are located on the Channel Islands (San Miguel, Santa Cruz, Anacapa, Santa Barbara, San Clemente) near Los Angeles, California, and San Benito, the Coronado and San Jerónimo islands off the coast of Baja California, Mexico. The Scripp's murrelet thus adheres to waters whose surface temperature is more than 12 degrees Celsius. Outside the breeding season, it lives on the open sea with a range north to central British Columbia southward to the tip of Baja California.

Breeding

The colonies are found on small, low-precipitation islands which have rocky coastlines. Most colonies are less than 600 feet from the coastline. The birds are monogamous, and mate for life. In one study, birds that were leg-banded used the same nesting site three years in a row. The individual nests are spread out, which is rather uncommon for alcid birds, which often breed in dense colonies.

Scripp's murrelets nest in rock niches or crevaces. The propagation time is relatively little synchronized. One study showed that Scripp's murrelets lay 80 percent of the eggs over a period of 24 to 47 days[4]. The earliest laying taking place on this island on February 22, with a peak in the period from March 21 to April 21. The last eggs were laid in the middle of June. The eggs are elliptic to oval and speckled grayish brown on a whitish to olive brown base and roughly speckled. On Santa Barbara Island 69 percent of the nests had two eggs, 25 percent of the eggs consisted of one egg. Larger clutches were also found, the possible results of nests used by two or more females. Egg incubation usually begins two days after the second egg is deposited. The brooding period is an average of 31 days. Chicks spend less than 48 hours in the nest after hatching before joining their parents in the sea, where they are fed and reared until fledged.


Threats

Gulls, owls, and falcons are among the natural predators, but the greatest impact in losses were made by introduced mammals to the islands via shipwrecks: rats and feral cats, which caused a decline in numbers on its breeding islands; on the island of Anacapa black rats nearly caused the extinction of the birds there. A program meant to remove non-native predators from their islands is somewhat successful, giving hope that the species can recover[5]. Man's nearby fishing activities at night plus pollution from nearby Los Angeles have also been cited as factors.

References

  1. http://oldredlist.iucnredlist.org/details/62101249/0
  2. https://www.biologicaldiversity.org/species/birds/Xantuss_murrelet/index.html
  3. https://www.fws.gov/ventura/docs/qa/Q&A%20Scripps%20and%20Guadalupe%20Murrelet%2012-month%20Findings_9.19.2016docx.pdf
  4. http://bio.research.ucsc.edu/people/croll/pdf/Wolf_2005.pdf
  5. https://www.audubon.org/news/how-two-secretive-seabirds-evaded-endangered-species-list