Harrier

Harriers are species of diurnal hawks. They are birds of prey. Harriers usually 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.
Details.
Most harriers are placed in the genus "Circus". This scientific name comes from the circling movements the birds make when courting.
Two other harriers are in the genus "Polyboroides", the "harrier-hawks", which are allopatric (geographically separated) and restricted to the Afrotropic ecozone. The remaining single species forms the genus "Geranospiza".
Ring-tails.
"Ring-tail" is an informal term used by birders for the juveniles and females of several harrier species. If seen in the field the exact species usually cannot be known. Ring-tail harriers include the juveniles and females of Montagu's harrier ("Circus pygargus"); Northern or hen harrier ("Circus cyaneus"); and pallid harrier ("Circus macrourus").