Circus is a genus of birds in the family Accipitridae. The genus includes most harriers which are of the several species of diurnal hawks.

1/ Pallid Harrier (Diều Bụng trắng, Circus macrourus)
2/ Eastern marsh harrier (Diều đầu trắng, Circus spilonotus)
3/ Pied harrier (Diều mướp, Circus melanoleucos) 
4/ Hen harrier (Circus cyaneus)

accipitrinus Latin accipitrinus hawk-like (accipiter: hawk).
In both Latin and Greek, the root of the word "circus" means "ring" or "circle". The Latin word circus comes directly from the Greek word κίρκος (kírkos), which also means "circle" or "ring". This etymology describes the shape of the ancient Roman arenas and the modern performance spaces where circuses are held.