The Vietnamese name for the larger herons is Chim diệc. The Night Heron (Nycticorax nycticorax) is called Chim vạc, reflecting its cry, and several similar-looking smaller herons and bitterns are also called by this name.
However, the most common name for the egrets, herons, and bitterns is Chim cò. This is a general term that is not used exclusively for the Ardeidae; it is also used for the storks and ibises.
Naturalists assign names to the ardeids as follows:
- Vạc (unmarked refers to Nycticorax nycticorax): Great Bittern (Botaurus) Night Herons (Gorsachius, Nycticorax)
- Diệc: Herons (Ardea)
- Cò: Bitterns (Ixobrychus, Dupetor) - Night Heron (Gorsachius — alternative name) - Herons (Butorides, Ardeola, Bubulcus) - Egrets (Ardea, Egretta)
Herons and bitterns are favorites for similes and folk expressions in Vietnamese.
The Chinese have a proverb: 鷸蚌相争，漁人得利 yù bàng xiāng zhēng, yúrén dé lì. ’The yu (= snipe) and the clam struggle; the fisherman profits’. This derives from an old story of a snipe/sandpiper who put his bill inside the clam’s shell in order to eat the clam. The clam countered by clamping its shell tightly onto the bird’s bill. The two were locked in a battle that neither could win. Along came the fisherman and claimed them both. The moral of the story is obvious.
Vietnamese has borrowed this proverb, but substitutes the cò for the snipe: Cò trai giữ nhau, ngư ông được lợi ’The heron and the mollusk hang on to each other, the fisherman gains the benefit’. (Vietnamese sometimes also substitutes a fight between a cockle and a clam, ngao sò.)