Hobby and kestrel are among the 60 varieties of birds of prey in the falcon family. Similarities in their body shape and color make it hard to tell them apart, especially without binoculars. I tend to leave mine at home, or lock them in the car, where they do me no good at all once I'm off wandering through the woods!!
There is one glaring difference you'd find if you were to travel to an area where both birds were common, which is their eating behavior.
Kestrels spend most of their time hovering or resting at roadsides. They generally spot their prey on the ground and stop to eat. Most of the similar looking birds you see hovering are either kestrels or something in the same family.
Hobbies, on the other hand, are mostly unable to hover. Constantly on the move, they grab smaller prey, such as dragonflies and other insects, with their open beak. Larger meals, including small birds, are caught in their talons and transferred to their mouth as they fly. Pairs of hobbies can even be seen feeding each other at great heights.
Hobbies are found primarily in Europe, Asia and Africa. Unfortunately for people in the United States, including me, they don't tend to live or visit here. However, a small falcon called the American Kestrel is extremely common throughout the North America and parts of South America. It lives year round in many states, and spends warm months in the Northeast, where I live, so I'm putting it on my list for next summer's viewing!