Which organisms would be the prey for the hawk?

Other hawks, eagles, owls can prey on them. The Goshawk is well known for removing any competitors from it's territory, even larger species. Large owls sometimes take hawks that are roosting at night or even when they are incubating eggs. Any type of cat, or dog, or marten, indeed any carnivorous mammal.

Small mammals like mice, voles, shrews, and gophers