Black-winged kite 
(Elanus caeruleus), also known as the black-shouldered kite

The black-winged kite (Elanus caeruleus), also known as the black-shouldered kite, is a small diurnal bird of prey in the family Accipitridae.

The name Elanus is from the Ancient Greek elanos for a "kite".
Latin caeruleus : dark blue likely from caelum, "sky";