Loggerhead Shrike (Lanius ludovicianus)

   
       The Loggerhead shrike is a medium-sized passerine with a grey back, black wings, white breast and a notable black mask around the eyes extending across the forehead. Although the Loggerhead shrike is a songbird, it has a predatory lifestyle. While shrikes have a strong, hooked beak resembling that of a bird of prey, they lack strong talons and must impale larger prey on thorny trees, or barbed wire. This serves a number of functions: it secures larger prey items while the shrike tears them into pieces that can be eaten; it provides a store of food; and it serves as a courtship display by males to attract females to a potentially successful mate and territory.
       
       The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) became concerned as to the status of the Loggerhead Shrike (Lanius ludovicianus) in the early 1980's and designated the eastern subspecies as threatened in 1985 (Cadman, 1985). Due to the continued decline in numbers, the small size of the remnant population and threats to the species' primary breeding sites, their status was upgraded to endangered in 1991, while the status of the Great Plains population was upgraded to threatened.

 Distribution and Abundance in Canada


        The Loggerhead shrike has a widespread distribution throughout North America, with three subspecies being found in Canada (Godfrey 1979). Lanius l. migrans, the Eastern subspecies, was formally found in Manitoba, Ontario, Québec, New Brunswick and Nova Scotia, but is now restricted only to southern Ontario. Lanius l. excubitorides, the Great Plains subspecies, breeds in southwestern Manitoba, central and southern Saskatchewan and Alberta. Lanius l. gambeli is a northwestern United States subspecies which has been recorded as a rare transient in British Columbia.

© Long Point Bird Observatory        Numbers of Loggerhead shrikes in eastern Canada have declined since 1900, especially in the last 25 years (Cadman 1985). Extensive annual surveys began in the core areas in 1992 to monitor the species' population. As shown to the left, the number of shrikes in the province has decreased substantially since then and the population is now at extreme risk of extinction in Ontario.

© Long Point Bird Observatory       The current wild population of migrans birds is estimated at 20-25 pairs situated entirely in southern Ontario. At present in Ontario, it breeds almost entirely in three core areas, all of which are located on limestone plains immediately adjacent to the Canadian Shield. The map to the right shows the approximate locations of these three core areas within the shrike's historic range in Ontario. The current wild population of excubitorides birds is estimated at close to 4000 situated in Alberta, Saskatchewan and Manitoba..
   
       The reasons for the decline in shrike numbers is unclear. Habitat loss has been suggested as a reason, however Cadman (1985) reported that numbers in the east had declined faster than had available habitat. Increased mortality due to habitat degradation on the wintering grounds, toxic chemical accumulation, collisions with automobiles, climatic factors, as well as human disturbance have also been implicated as possible causes contributing to declines (Cadman, 1985; Gawlick and Bildstein, 1990).

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Captive Breeding of Loggerhead Shrikes at the ASCC


       In 1992, the ASCC established a colony of western Loggerhead Shrikes (Lanius ludovicianus excubitorides) using 19 young collected from Saskatchewan. Between 1994 and 1996, this colony was used to develop management and captive breeding techniques for the critically endangered eastern subspecies (L. l. migrans).  In 1997, 15 wild shrike nestlings were collected, and 8 were raised at the ASCC by curator Ian Ritchie. The remaining 7 went to the Toronto Zoo, the other main partner in this important  breeding effort. Work at both facilities has found that collecting young at eight to 10 days of age is the most effective way of obtaining a breeding stock. At the ASCC, once the young have been hand-reared to the fledging stage, they are transferred to large flight rooms where various young birds grow up together until the onset of winter. They are then moved to individual holding pens in a heated room for the winter.
       
       1998 saw the first season of captive breeding of the migrans subspecies at the ASCC. In mid-April birds are paired according to genetic background and each pair is placed in a large, outdoor breeding pen. As in indoor pens, facilities are fitted with hawthorn bushes, barbed wire, nesting trees and bathing water.  From the original 8 birds collected by the ASCC, three breeding pairs were set up in the spring of 1998 at the ASCC and they successfully produced four chicks. These four, along with 16 additional wild chicks collected by the centre during 1998, form the nucleus of a large captive breeding colony for 1999.


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References


Cadman, M.D. 1985. Status report on the Loggerhead Shrike (Lanius ludovicianus) in Canada. COSEWIC report, Ottawa, Ont.

Canadian Wildlife Service. 1993. Loggerhead Shrike. Hinterland Who's Who publication. Environment Canada.

Chabot, A.A., R.D. Titman and D.M. Bird. 1995. Habitat selection and breeding biology of Loggerhead Shrikes in Eastern Ontario and Québec. in Yosef, R. and F.E. Lohrer (Editors). Shrikes (Laniidae) of the world: Biology and Conservation. Proceedings of the Western Foundation of Vertebrate Zoology 6(1):155-156.

Gawlick, D.E. and K.L. Bildstein. 1990. Reproductive success and nesting habitat of Loggerhead Shrikes in North-Central South Carolina. Wilson Bull. 102(1): 37-48.

Godfrey, W.E. 1979. The Birds of Canada. National Museum of Natural Sciences, Ottawa, Ont.

Haas, C.A. and S.A. Sloane. 1989. Low return rates of migratory Loggerhead Shrikes: winter mortality or low site fidelity? Wilson Bull. 101: 458-460.

Johns, B., E. Tefler, M. Cadman, D.M. Bird, R. Bjorge, K. DeSmet, W. Harris, D. Hjertaas, P. Laporte, R. Pittaway. 1994. National Recovery Plan for the Loggerhead Shrike. Report No. 7. Ottawa: Recovery of Nationally Endangered Wildlife Committee. 32 pp.

Long Point Bird Observatory. 1997. Endangered Loggerhead Shrikes and other grassland birds: a landowner's resource guide. Canadian Wildlife Service, Long Point Bird Observatory. 11pp.

Robert, M. 1989. Les oiseaux menacés du Québec. Environment Canada, Canadian Wildlife Service, Quebec City, Que.

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