The northern shoveler can be spotted within Oklahoma during the spring/fall migration and throughout the winter months (as Oklahoma falls within their winter range).
I’ve been lucky to be able to spot a northern shoveler (or two) a time or two on Boomer Lake. Occasionally it has been just a single male in the spring slowly making his way back to their breeding territory. Other times, it has been a small flock of both males and females swimming around the lake.
The most distinctive feature of this duck is its beak.

The beak looks like a shovel (hence the name, shoveler), and upon closer examination there are approximately 110 fine lamellae (or little projections) along the edge. I’ll take the word of the various wildlife biologists that have gotten that close. to be able to count them.
These lamellae act like a colander allowing the duck to filter out its meals.
There is also a distinct color pattern difference between the sexes.
Breeding males have a bold color pattern of white, blue, green, and rusty red. Their heads are green; they have a white chest and flanks, with a rusty red patch. The blues and greens on the wings are noticeable during flight.

Females (and immature males) have a more mottled brown coloring, and light blue tinges on the wings that are visible during flight.
The northern shoveler can be spotted somewhere within North America at any point during the year.

Their main ‘breeding’ areas include Alaska, parts of Canada, and parts of several states (such as Washington, Idaho, Montana, Wyoming, the Dakotas, and Minnesota).
Numerous other states are within their migration routes, and others are where they spend the winter. There are are few areas out west where they may be found year-round (western Oregon, and parts of Nevada, Utah, California, and Colorado).
During the breeding season, they can be found along shallow wetlands (as they like to nest along the edges and in the nearby grassy fields).
During the rest of the year they can be found foraging in salt-marshes, estuaries, lakes, wetlands, agricultural ponds, flooded fields, and wastewater ponds.
To spot these birds–look for the males first, they’re more colorful and of course look for the unique beak.

The diet of these birds consists of seeds and tiny crustaceans and aquatic invertebrates. They make use of their colander and shovel-like beak to go after the really small things that they can filter from the water (and other ducks ignore).
Two other little tidbits on the northern shoveler:
Northern Shovelers are also found in the ‘Old World’. Their breeding grounds are across northern Europe, and the will winter in southern Europe, Africa, and India.
Males will gather in small flocks before heading south, as they tend to molt their flight feathers prior to the start of the fall migration. Since they are then temporarily ‘flightless’, they tend to stay close to the vegetation and in groups for protection.
Reference: https://www.allaboutbirds.org/guide/northern_shoveler