Even meadowlark and peregrine falcon have been documented taking eggs and chicks. Mammalian predators, primarily red fox and skunk, cause enormous damage by eating eggs and, in the case of the fox, caching eggs for later meals. Nesting islands help to reduce predation by mammals. The islands work best for deterring skunks and cats, although red foxes are capable of swimming to islands. Islands have not proven to be consistently effective where a broad range of predators exists.
Islands also create a high personnel load on a yearly basis for vegetation removal.
The manual clearing of islands as small as 2 acres can be extremely time consuming without mechanical equipment. Islands offer no protection from avian predators, which easily fly to the islands from adjacent land. Live-trapping of kestrels by using Balchatri traps has been very successful. Pole traps and direct shooting are utilized where it is virtually impossible to use live-traps. Chain-link fences have been used successfully at a number of colonies to deter mammalian predators.