Welcome to "Cooper's Diner". This Cooper's Hawk (Accipiter cooperii) stops at the feeder occasionally to see if he can snatch an unwary songbird. I have yet to see him succeed in grabbing a light snack (pardon the pun). If I am watchful enough I know I'll someday get to see him catch a bird.
Cooper's Hawks have the nickname "chicken hawk" because one of their favorite meals is also one of our favorite meals...chicken. Birders don't always appreciate hawks attacking the songbirds they feed, but we must realize that all birds play an important role in the avian world-predator and prey alike.
I welcome all birds to my yard with the exception of two: House (European) Sparrows and European Starlings. Both are non-native species introduced in the last century. Since they are non-native, trapping and killing them is not only legal but in some localities, encouraged. If you think it's cruel, you should read up on how House Sparrows invade the nests of our native songbirds and kill the young, toss eggs out and even kill the adults if they are lucky enough to trap one inside a nest box. Starlings compete with our native owls, woodpeckers and flickers for nesting cavities. These two species are a perfect example of what can happen when we introduce exotic species into our habitats.
Fortunately, raptors like the Cooper's Hawk, Sharp-Shinned Hawk, and American Kestrel are very adept at capturing small birds like House Sparrows and Starlings. It is best if mankind leaves nature alone to follow its natural course. Things go terribly awry when we interfere and try to manage nature.