Green-Winged Teal

 The Green -Winged Teal has a small compact body, rounded head.  Their bill are short and thin.
The male has a chestnut head with a green patch a white bar on each flank.  Females has a dull body and head, with a black bill with dull orange edges and a pale line on the sides of the undertail coverts and a white belly.
They are common and wide spread.

DesertDale took this photo at El Cajon.