This is another migrant duck that passes through Oklahoma during both the spring and fall migrations.
I’ve only managed to spot these birds once or twice (usually during the spring migration) as they make their way from their winter grounds back to their breeding grounds.

In terms of coloring, there is a difference between the sexes (mainly during the breeding season).
Males have brown bodies with speckles on the chest. Their heads are slaty-blue color with a white crescent behind the beak and a small white patch near their rears.
Females (and non-breeding males) have feathers in different shades of brown that result in a patterned look on their chest and back. Females also have an eye line, and their beak is black (there is no white crescent around the beak).

The blue-winged teal can be spotted across most of North America during the year. Though they are absent from the interior portion of California, a good chunk of Nevada, Utah, and Arizona. Majority of North America falls within their breeding zone, while are parts are either within their migration zone or their wintering zone.
They will migrate all the way down into Central and South America for the winter, making them one of the most long-distant migratory birds in the western hemisphere.
These birds prefer shallow ponds or pond-marsh mixes during the summer; marshes, wetlands around lakes, and rice fields (preferring fresh or brackish water areas over saltwater) during migration; during the winter (in the US) they prefer wetlands/marshes.

Therefore, the best place to see them is along the edges of lakes, or in the shallow parts of marshes and wetlands.
The diet of blue-winged teals is varied. They will eat aquatic insects, crustaceans, clams, and snails in addition to vegetation and grains. Females that are preparing to lay eggs will eat more of the insects, crustaceans, clams, and snails (since those are richer in protein).
Their winter diets consists mostly of seeds and grains.
Two weird facts about the blue-winged teal:
Unlike other ducks that leave early for their breeding grounds, the blue-winged teal are among the stragglers that migrate later in the spring northwards. Though they’re one of the first ducks to head south for the winter.
They are the second most abundant duck in North America after the mallard.
Reference: https://www.allaboutbirds.org/guide/blue-winged_teal