A very small raptor hovering above an open field is likely a?

The American Kestrel is a small falcon often seen hovering in open fields while hunting. This behavior is distinctive to the species, as they utilize a technique known as "kiting," where the bird remains stationary in the air while looking for prey, typically small insects or mice. Their size—being the smallest falcon in North America—contributes to their ease of hovering without excessive flapping.

Meanwhile, the Sharp-shinned Hawk and Cooper's Hawk are typically more woodland predators; they prefer to chase smaller birds in forested areas rather than hover in open fields. The Merlin, while also a small raptor, is more agile and focuses on rapid pursuits rather than the hovering stance indicative of the Kestrel. Hence, among the options provided, the American Kestrel clearly stands out as the most likely candidate for hovering above an open field.