Predator management for the protection of the endangered California least tern (Sterna antillarum brownii) and documentation of bullsnake (Pituophis catenifer) predation in San Diego County, California

The endangered California least tern is a seasonal migrant that nests in colonies on coastal estuaries and beaches of California. A variety of native and non-native predators prey on nesting terns and have the potential to devastate nesting colonies. USDA APHIS Wildlife Services (WS) conducts an annual program to reduce predation and protect nesting terns. Management activities include monitoring and removing known and potential predators with the selective use of various trapping and removal techniques. The most common predators managed at nesting colonies include feral cats, striped skunks, Virginia opossums, California ground squirrels, common ravens, western gulls, American kestrels, and barn owls. However, during the 2003 nesting season, WS documented the loss of 61 least tern nests due to predation by bullsnakes at a colony at North Fiesta Island in Mission Bay, San Diego County. This paper gives an overview of the WS predator management program for the protection of the endangered least tern and describes the nature and management of predation by bullsnakes.