Xantus’s murrelet (Synthliboramphus hypoleucus)

Description

Xantus’s murrelet fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Xantus’s murrelet description

This small marine bird belongs to the genus Synthliboramphus, a group of seabirds remarkable for the fact that they are the only seabirds which rear their young entirely at sea ⁽³⁾. Xantus’s murrelet has striking black and white plumage: black on the upperparts, sometimes tinted faintly with grey as the feathers become worn, and snowy white on the underside. The flanks may be white or mottled grey and white, the legs are bluish-grey, and the feet bear black claws ⁽²⁾. Two subspecies of Xantus’s murrelet are recognised: Synthliboramphus hypoleucus hypoleucus and Synthliboramphus hypoleucus scrippsi. The former can be recognised by the prominent white crescents above and below the eye, while the white patterning on the face of S. h. scrippsi is very indistinct ^{(2) (4)}. Female Xantus’s murrelets are usually larger than the males, while juveniles may be distinguished by the scattered dark barring along the flanks ⁽²⁾. This seabird calls with a shrill whistle ⁽⁴⁾.

Synonyms

Brachyramphus hypoleuca, Brachyramphus hypoleucus.

Size

Length: 23 – 25 cm ⁽²⁾

Wingspan: c. 40 cm ⁽²⁾

Average weight: 148 - 167 g ⁽²⁾

Chick weight: c. 25 g ⁽²⁾

Xantus’s murrelet biology

Xantus’s murrelet is thought to be a monogamous bird which arrives at its island breeding colony around mid-February, about three weeks before it lays its eggs. The female lays two eggs, eight days apart, into a crevice in a cliff, at the back of a small cave, under a boulder, or occasionally, on bare ground beneath thick vegetation ⁽²⁾. Following the laying of the second egg, the male and female will take it in turns to incubate the eggs for the next 34 days. During this time, the eggs are highly vulnerable to predation by deer mice (Peromyscus maniculatus) ⁽²⁾. The chicks are very well-developed on hatching, with limbs that are already 98 percent of the size of adults’ ⁽⁵⁾, and are taken to sea, just one to two days later, by their parents ⁽²⁾. Here, unique to Synthliboramphus, the remainder of the chick’s development takes place ⁽⁶⁾.

In April or May, Xantus’s murrelet will move north and west, away from the breeding islands, travelling rather slowly to their wintering areas where they will remain until late November or early December ⁽²⁾. Xantus’s murrelet feeds mainly on larval fish, as well as other small prey such as sandeels and crustaceans ⁽²⁾. Diving down to maximum depths of 21 metres and remaining underwater for up to 28 seconds, Xantus’s murrelet uses its wings to propel itself through the water to pursue and capture its prey ⁽⁷⁾. During the breeding season, northern anchovies (Engraulis mordax) comprise a significant part of this murrelet’s diet, and thus breeding effort has been noted to be lower when anchovy abundance is low ⁽²⁾.

Xantus’s murrelet range

Xantus’s murrelet breeds off the coast of southern California, USA, and Baja California, Mexico ⁽⁴⁾. The two subspecies have different breeding ranges, overlapping only on the San Benito Islands off Baja California. S. h. scrippsi breeds on the southern California Channel Islands and on islands off the west coast of Baja California, while S. h. hypoleucus breeds only off Baja California, on the three San Benito Islands and on two rocks offshore of Guadalupe Island. Previously, more breeding colonies may have existed on other islands, before they were destroyed by invasive animals ⁽⁴⁾. Outside of the breeding season, this small seabird ranges from the southern tip of Baja California, north to British Columbia, Canada ⁽²⁾.

See this species on Google Earth.

Xantus’s murrelet habitat

Breeding on steep cliffs above the sea, as well as on slopes and canyons ⁽²⁾, Xantus’s murrelet selects areas where there is a sparse cover of shrubs and herbs ⁽⁴⁾. During winter, this bird can be found offshore, in the warm waters of the California Current ⁽²⁾.

Xantus’s murrelet status

Classified as Vulnerable (VU) on the IUCN Red List ⁽¹⁾.

Xantus’s murrelet threats

One of the most significant threats to this Vulnerable bird is the impact of invasive mammals, including feral cats, black rats and house mice, which prey on the eggs, young, and occasionally adults of Xantus’s murrelet ^{(4) (8) (9)}. The extinction of some breeding colonies in the past as a result of invasive mammals demonstrates the devastating affect that they can have on this species ⁽⁴⁾.

In addition to the threats of invasive species, Xantus’s murrelet could be affected by oil spills, drowning in fishing gear, pollution, and disturbance of nesting sites ⁽⁴⁾. In the future, changes in sea temperature caused by global climate change may also have a detrimental impact on this species if it alters the availability of prey, such as the northern anchovy ⁽⁴⁾.

Xantus’s murrelet conservation

Since the mid-1990s, introduced mammalian predators have been removed from several of the murrelet’s nesting islands ^{(8) (10)}, such as the eradication of black rats from Anacapa Island, California, with Xantus’s murrelet showing encouraging signs of recovery as a result ⁽¹¹⁾. In 2003, fishing was banned within certain areas of the Channel Islands National Marine Sanctuary, which may help reduce noise and light pollution around breeding colonies. Guadalupe Island of Mexico has recently been declared a Biosphere Reserve and the other Mexican islands on which Xantus’s murrelet nests are situated either within existing biosphere reserves or in a proposed new biosphere reserve. These measures should hopefully mitigate the negative impacts related to commercial fisheries and tourism ⁽⁴⁾. In 2005, a special symposium titled “Biology and Conservation of the Xantus’s Murrelet” was held, with the aim of increasing awareness of the plight of this species, and to promote the publication of recent findings on its biology and status ⁽¹⁰⁾. Such efforts are very encouraging for this threatened seabird, but future conservation actions are still required, including continued efforts to remove the threat of introduced mammals from further critical breeding islands ^{(4) (8)}.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For further information on conservation of Xantus’s murrelet see:

• National Audubon Society:
  http://audubon2.org/watchlist/viewSpecies.jsp?id=224

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org

Authentication

Glossary

Crustaceans

Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.

Flanks

The sides of the body between the ribs and the hips.

Larval

Of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Monogamous

Having only one mate during a breeding season, or throughout the breeding life of a pair.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

References

1. IUCN Red List (October, 2007)
   http://www.iucnredlist.org
2. del Hoyo, J., Elliott, A. and Sargatal, J. (2002) Handbook of the Birds of the World. Volume 3: Hoatzin To Auks. Lynx Edicions, Barcelona.
3. Gaston, A.J. (1994) Ancient Murrelet (Synthliboramphus antiquus). In: Poole, A. (Ed) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
   http://bna.birds.cornell.edu/bna/species/132
4. Birdlife International (July, 2008)
   http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3311&m=0
5. Hall, B.K. (2005) Bones and Cartilage. Academic Press, London.
6. Ydenberg, R.C., Clark, C.W. and Harfenist, A. (1995) Intraspecific fledging mass variation in the Alcidae, with special reference to the seasonal fledging mass decline. The American Naturalist, 145(3): 412 - 433.
7. Hamilton, C.D., Golightly, R.T. and Takekawa, J.Y. (2005) Characteristics of diving in radio-marked Xantus’s murrelets. Marine Ornithology, 33: 155 - 159.
8. Keitt, B.S. (2005) Status of Xantus’s murrlet and its nesting habitat in Baja California, Mexico. Marine Ornithology, 33: 105 - 114.
9. National Audubon Society (September, 2008)
   http://audubon2.org/watchlist/viewSpecies.jsp?id=224
10. Carter, H.R., Sealy, S.G., Burkett, E.E. and Piatt, J.F. (2005) Biology and conservation of Xantus’s murrelet: discovery, taxonomy and distribution. Marine Ornithology, 33: 81 - 87.
11. Whitworth, D.L., Carter, H.R., Young, R.J., Koepke, J.S., Gress, F. and Fangman, S. (2005) Initial recovery of Xantus’s murrelets following rat eradication on Anacapa Island, California. Marine Ornithology, 33: 131 - 137.