San Clemente Loggerhead Shrike
San Clemente Loggerhead Shrike
Lanius ludovicianus mearnsi
|Listed||August 11, 1977|
|Description||A medium-sized passerine (or perching) bird.|
|Habitat||A variety of terrestrial habitats.|
|Food||Smaller birds, mammals, reptiles, and arthropods.|
|Reproduction||Lays eggs in a nest in a shrub.|
|Threats||Predation by introduced mammals, and habitat destruction by introduced goats.|
The San Clemente loggerhead shrike is a medium-sized passerine (or perching) bird. It has short, rounded wings that are slightly shorter than its tail. Its plumage coloration is gray on the back, white on the throat and belly, with black and brown markings, including a black mask covering the ocular region of the head. It has a stout beak, with a so-called tomial tooth on each side of the upper mandible. Compared with other subspecies of Lanius ludovicianus, it has a shorter bill and shorter wings, a darker gray back, whiter rump, generally lighter breast and flanks, and more white on the scapular wing feathers.
The San Clemente loggerhead shrike is a predator of small birds, mammals, reptiles, and arthropods. It establishes a defended home range during the breeding season, ranging from about 100-250 acres (40-100 hectares) in area. The nest is constructed in a shrub, and the typical clutch size is about five eggs. Both adults incubate the eggs and care for the young. Standing dead trees (or snags) are used as perches for feeding, searching for prey, as places to impale prey on sharp twigs, and as perches during singing.
The San Clemente loggerhead shrike inhabits dry habitats of a type referred to as maritime desert scrub and maritime sage scrub. It also forages in other terrestrial habitats on San Clemente Island, including wooded ravines and canyons.
The San Clemente loggerhead shrike is a locally evolved (or endemic), non-migratory subspecies that occurs only on San Clemente Island, off the coast of southern California.
Only about 20 breeding pairs of the San Clemente loggerhead shrike survived in the late 1990s. The most important factors limiting its abundance and distribution appear to be high rates of predation of breeding adults and recently fledged young, and a shortage of suitable nest shrubs over the northern half of San Clemente Island. The predation appears to be due to introduced domestic cats (Felis catus ), black rats (Rattus rattus ), and native predators. The lack of shrubs is the result of browsing by introduced feral goats (Capra hircus ). In addition, the shrike and its habitat are threatened by habitat destruction and disturbance associated with various military activities on San Clemente Island. These include military research, development and testing of undersea weapons, instrumentation, and communications. Other military activities include simulated aircraft carrier landing practices, ship-to-shore gunnery exercises, amphibious landing exercises, and troop maneuvers involving up to 4,000 people.
Conservation and Recovery
San Clemente Island is protected against full development, although many military uses continue. The most important needs for conservation of the San Clemente loggerhead shrike are the eradication of non-native goats, cats, and rats. The Department of the Navy has attempted to undertake a goat-eradication program, with the full support of conservation and ecology interests. However, the goat eradication has been hampered by opposition from animal-rights groups. These groups succeeded in stopping a goat shooting program and replacing it with much less-effective, live capture techniques. Nevertheless, the population of goats has been greatly reduced, and they may yet be eradicated. However, the population of feral cats, which are devastating predators of the endangered logger-head shrike, has yet to be reduced.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
U. S. Fish and Wildlife Service, Ventura Field Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766
Fax: (805) 644-3958
Conservation Management Institute. 14 March 1996."San Clemente loggerhead shrike." Virginia Tech, Endangered Species Information System. (http://fwie.fw.vt.edu/WWW/esis/lists/e101008.html). Date Accessed: July 6, 2000.