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Loggerhead shrike
The loggerhead shrike (''Lanius ludovicianus'') is a passerine bird. It is the only member of the shrike family endemic to North America; the related northern shrike (''L. excubitor'') occurs north of its range but also in the Palearctic. It is nicknamed the butcherbird after its carnivorous tendencies, as it consumes prey such as amphibians, insects, lizards, small mammals and small birds.〔Craig R. 1978. An analysis of the predatory behavior of the Loggerhead Shrike. The Auk. 95(2): 221-234.〕 Due to its small size and weak talons, this predatory bird relies on impaling its prey upon thorns or barbed wire for facilitated consumption.〔Smith S. 1973. Aggressive display and related behavior in the loggerhead shrike. The Auk. 90(2): 287-298.〕 The numbers of Loggerhead Shrike have significantly decreased in recent years, especially in Midwest, New England and Mid-Atlantic areas.〔Lymn N, Temple S. 1991. Land-use changes in the Gulf coast region: links to declines in Midwestern loggerhead shrike populations. The Passenger Pigeon. 53(4): 315-325.〕
==Description==
The Loggerhead shrike is a medium-sized passerine.〔Chapman F. 1904. Handbook of birds of eastern North America. 6th edition. New York (NY): Appleton and Company.〕 "Loggerhead" refers to the relatively large size of the head as compared to the rest of the body. It measures approximately 9 inches from bill to tail. The wing and tail length is about 3.82 and 3.87 inches long, respectively.〔 It weighs on average 50 grams, with a range of 45-60 grams for a healthy adult shrike.〔Craig R, DeAngelis D, Dixon K. 1979. Long- and short-term dynamic optimization models with application to the feeding strategy of the loggerhead shrike. The American Naturalist. 113(1): 31-51.〕 The adult plumage of the Loggerhead Shrike is grey above, with a white to pale grey breast and black tarsi and feet. The bird possesses a black mask that extends across the eyes to its bill, unlike that of the similar but slightly larger northern shrike. The wings are black, with a distinct white patch on the primaries. The tail is black edged with white and the irises are brown.〔Chabot A. 1994. Habitat selection and reproductive biology of the loggerhead shrike in eastern Ontario and Quebec. Montreal (QC): McGill University Libraries.〕 The beak is short, black, and hooked, and contains a tomial tooth to help tear into prey.〔Miller A. 1931. Systematic revision and natural history of the American shrikes (Lanius). University of California Publications in Zoology. 38(2): 11-242.〕 It is difficult to sex an adult Loggerhead Shrike in the field, as they are sexually monochromatic.〔Sustaita D, Owen C, Villarreal J, Rubega M. 2014. Morphometric tools for sexing loggerhead shrikes in California. The Southwestern Naturalist. 59(4): 562-569.〕 However, several studies have reported sexual dimorphism in plumage and size traits.〔〔〔Collister D, Wicklum D. 1996. Intraspecific variation in Loggerhead Shrikes: sexual dimorphism and implication for subspecies classification. The Auk. 113(1): 221-223.〕 Juveniles possess a paler gray plumage that is subtly vermiculated.〔Alderfer J, editor. 2005. Complete birds of North America. Washington: National Geographic.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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