Merlins, also called pigeon hawks, breed in the northern Holarctic, with some migrating to subtropical and northern tropical regions in winter. In recent decades, merlin populations in North America have been significantly increasing, with some merlins becoming so well adapted to city life that they forgo migration. Swift fliers and skilled hunters, merlins specialize in preying on small birds. If you have seen them in your neighborhood, it may explain why your bird feeder is seeing very little action.