Bufflehead

I saw my first bufflehead in January 2021 at the Salton Sea, a male, and had no idea what it was. I've since seen quite a few more. Males are black and white with a large white patch behind the eye, and in good light, the black on the head can shine an iridescent purple and green. The back is black and the chest and flanks are white. 

This male, at Lake Silverwood, has a mostly purple sheen, but a little bit of green at the back of the head near the neck. 

This male, at Bolsa Chica in Huntington Beach, has much more green on the head. 

This male, at Bolsa Chica, is in more sunlight and has a more iridescent sheen. 

Females are more gray than black (blackish gray on the back and whitish gray on the chest and flanks) and have a much smaller white patch on the cheek (a little bit behind and below the eye). 

These females are at Bolsa Chica.

These females are at Bear River Migratory Bird Refuge. 

It is small and extremely active, diving almost constantly. It is a sea duck, but can be found in both salt and fresh water. It may be the most fun duck to observe because of its odd appearance and constant activity.   

Diving at Bolsa Chica.

Female and male flying at Aransas NWR in Texas.