Ardea is a genus of herons. 

1/ Great egret (Cò ngàng lớn, Ardea alba), also known as the common egret, large egret, or (in the Old World) great white egret or great white heron
The scientific name comes from Latin ardea for "heron", and alba for "white".
formerly placed in Egretta genus.

2/ Intermediate egret, median egret, smaller egret or medium egret (Cò ngàng nhỏ, Ardea intermedia)
Some authorities classify the intermediate egret in its own monotypic genus, Mesophoyx, while others place it with the smaller egrets in Egretta.

3/ Purple heron (Diệc lửa, Ardea purpurea) 
4/ Great-billed heron (Diệc Sumatra, Ardea sumatrana)
5/ Grey heron (Diệc xám, Ardea cinerea)

The below two species used to belong to the genus Bubulcus
6/ Eastern cattle egret (Ardea coromanda)

7/ Western cattle egret (Ardea ibis)

The genus name comes from the Latin word ardea meaning "heron".