Chroicocephalus is a genus of medium to relatively small gulls which were included in the genus Larus earlier.
The genus name Chroicocephalus is from Ancient Greek khroizo, "to colour", and kephale, "head".

1/ Black-headed gull (Chroicocephalus ridibundus)
The specific ridibundus is Latin for "abundant".

2/ Brown-headed gull (Mòng bể đầu nâu, Chroicocephalus brunnicephalus)