Evolution and systematics

The origin of shrikes is not known for certain. A fossil of a shrike-like bird (Lanius miocaenus) found in Lower Miocene deposits in France, indicates that the genus Lanius existed in Europe 25-30 million years ago. African origins have been suggested by various authors who consider that, out of the 74 species classically retained in the shrike family, only 10 have no link with Africa. These birds all belong to the genus Lanius, which still has nine endemic species on the African continent and may well have invaded Eurasia, where it also radiated.

The theory of African shrike origins, however, has recently been questioned, as molecular studies suggest that shrike ancestors originated in the Australasian region. From there, as Australia drifted northwards some 20-30 million years ago in the Tertiary period, shrikes might have emigrated to Asia.

Shrikes probably arrived much later in North America, where the loggerhead shrike (L. ludovicianus) may represent a first wave of shrike immigrants to the New World. L. ludovicianus may have been pushed south by a glacial epoch and was later followed by another wave of birds in the northern parts of the continent. It may be these birds that are now regarded as a race of the northern shrike (L. excubitor), which has a large holarctic distribution. The more common and widespread west-palearctic red-backed shrike (L. collurio) may be a much more recent invader, or re-invader, of northern latitudes after the retreat of the last glaciers about 12,000 years ago. Its typical migration pattern may reflect the route of its progressive northward spread. Its resident ancestor in Africa could be the very similar Emin's shrike (L. gubernator), known today from a belt spreading from central-west Africa to central-east Africa.

The most widely accepted standard sequence for recent birds dates back to the 1960s. It recognizes four subfamilies in the Laniidae, with 74 species in all. The subfamilies and the genera concerned are the following:

• Prionopinae (helmet-shrikes): Eurocephalus (two species); Prionops (seven species)

• Malaconotinae (bush-shrikes): Lanioturdus and Nilaus (monotypic); Dryoscopus (six species); Tchagra (six species); Laniarius (10 species); Telophorus (10 species); Malaconotus (five species)

• Laniinae ("true" shrikes): Corvinella (two species); Lanius (23 species)

• Pityriasinae (Bornean bristlehead): Pityriasis (one species)

Recent studies of genetic material and behavior, as well as observations of morphological and plumage characteristics, however, suggest that the above classifications may not reflect the true relationships among shrikes. Lefranc (1997) and Harris (2000) have suggested alternate taxonomies.

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