Two species of shrikes occur in North America, but only the Loggerhead Shrike (Lanius ludovicianus) is unique to this continent. Shrikes differ from other songbirds in that their diet regularly includes small vertebrate prey. In the absence of a raptorial foot used by larger predatory birds to handle live prey, shrikes have evolved the unique tactic of impaling prey on sharp objects such as thorns and barbed wire. This behavior has earned the species the nickname 'butcherbird'.
Between seven and eleven subspecies of the Loggerhead Shrike have been identified based on range, morphology and plumage coloration. In Alberta, the Loggerhead Shrike is included on the Yellow List of species that are not at immediate risk of extirpation, but may require specific management attention because of concerns about long-term population declines. Loggerhead Shrikes are considered threatened in western Canada by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 1999).
Loggerhead Shrikes are birds that love open places. Throughout their range, their habitat typically includes grasslands interspersed with scattered trees and shrubs that provide nesting and perching sites. A variety of habitats often occur within breeding territories, including cultivated cropland, transportation rights-of-ways, and shelterbelts. Shrikes typically hunt from dead trees, tall shrubs, utility wires and fences, and may impale their prey on sharp twigs, thorns, or barbed wire. These features may also be important components of habitat selection by the Loggerhead Shrike.
The Loggerhead Shrike is a medium-sized songbird. In the southern parts of the species' range, the Loggerhead Shrike is a permanent resident, but in more northerly areas, including Alberta, the species is migratory. Males arrive on the breeding grounds before females. Nests are built in a variety of trees and shrubs. The female, alone, builds the nest over a period of six to eleven days. The nest, which is generally a bulky cup of rootlets, forbs and bark strips lined with finer material, is generally concealed below the crown in a crotch or on a large branch.
Loggerhead Shrikes consume a wide variety of vertebrate and invertebrate prey, and appear to adjust diet to local prey availability. Numerically, invertebrates make up the largest part of the diet, especially during the breeding season. Vertebrates make up a larger part of the winter diet and probably make up the greatest percentage of biomass of the diet at all times of the year. Generally, small mammals and birds make up the majority of vertebrate prey, although small reptiles and amphibians are also consumed. In Alberta, vertebrate prey are primarily Thirteen-lined Ground Squirrels, Meadow Voles, and Sagebrush Voles.
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