What is a defining characteristic of true falcons?

A defining characteristic of true falcons is their "toothed" or "notched" beak. This distinctive feature assists falcons in their predatory behavior. The notch allows them to effectively grip and kill their prey, which typically consists of smaller birds and sometimes small mammals or insects. The shape and design of the beak is specialized for their hunting style, enabling them to be efficient predators.

In terms of the other options, while some birds of prey may possess heavy crushing feet, it is not a defining feature of true falcons; rather, they are known for their sharp talons adapted for catching and killing. Feeding habits can vary among different species, so while true falcons often feed on birds, it is not exclusive to them. Additionally, true falcons are indeed highly maneuverable, but this characteristic is more broadly shared among various birds of prey, making it less distinctive than the unique beak structure.