A harrier is any of the several species of diurnalhawks sometimes placed in the subfamily Circinae of the bird of preyfamilyAccipitridae. Harriers characteristically hunt by flying low over open ground, feeding on small mammals, reptiles, or birds. The young of the species are sometimes referred to as ring-tail harriers. They are distinctive with long wings, a long narrow tail, the slow and low flight over grasslands and skull peculiarities. The harriers are thought to have diversified with the expansion of grasslands and the emergence of C4 grasses about 6 to 8 million years ago during the Late Miocene and Pliocene.[1]
Ring-tail is an informal term used by birders for the juveniles and females of several harrier species when seen in the field and not identifiable to an exact species.[7] Ring-tail harriers include the juveniles and females of Montagu's harrier (Circus pygargus), hen harrier (Circus cyaneus), and pallid harrier (Circus macrourus).
The subfamily Circinae has traditionally included the genera Polyboroides and Geranospiza which include three species: the Madagascar harrier-hawk, (Polyboroides radiatus), the African harrier-hawk, (Polyboroides typus) and the crane hawk, (Geranospiza caerulescens). This may however not be a valid subfamily as the monophyletic genus Circus is nested within the Accipiter groups while the other two genera are paraphyletic and are part of the larger Buteonine clade. Many species in the genus Circus show very low diversity in their mitochondrial DNA due perhaps due to extreme drops in their populations, which are prone to fluctuations with varying prey densities.[10][11]
References
^Oatley, Graeme; Simmons, Robert E.; Fuchs, Jérôme (2015). "A molecular phylogeny of the harriers (Circus, Accipitridae) indicate the role of long distance dispersal and migration in diversification". Molecular Phylogenetics and Evolution. 85: 150–60. doi:10.1016/j.ympev.2015.01.013. PMID25701771.
^Griffiths, Carole S.; Barrowclough, George F.; Groth, Jeff G.; Mertz, Lisa A. (2007). "Phylogeny, diversity, and classification of the Accipitridae based on DNA sequences of the RAG-1 exon". Journal of Avian Biology. 38 (5): 587–602. doi:10.1111/j.2007.0908-8857.03971.x.
