The least Bell's Vireo is listed on the Federal Endangered Species List.The vireo's preferred habitat is the lower portions of riparian growthin the vicinity of water.  The destruction of this habitat in manyareas, combined with habitat degredation and the introduction of speciesunsuitable for vireo nests (especially Arundo donax),have been a major factor in the decline of the species.

The Southwestern Willow Flycatcher ( Empidonax traillii extimus) isa smaller bird currently recognized by both the Federal Government andthe State of California as endangered. Once common, in 1987 only 300-500nesting pairs remained.  Since that time, virtually all monitorednesting groups have continued to decline.  Habitat loss, combinedwith increased predation by cowbirds has been theprimarily responsible for this decline.

The riparian (streamside) vegetation where the southwestern willow flycatchernests has been degraded, and much of it has been destroyed. Removal ofvegetation to clear land for agriculture, the invasion of non-native speciessuch as Arundo and Saltcedar, and the alterationof hydrology by humans have all contributed to the loss of riparian vegetation.The Santa Ana Watershed is dedicated to the eradication of Arundo and Saltcedearthroughout the watershed to preserve the riparian habitat for these species.

The Santa Ana Sucker is a small fish that wascommon in the Santa Ana Watershed. Changes in the Santa Ana Sucker's habitat,especially through water diversions, stream channelizations, erosion, andpollution, have been the prime cause in the decline of the species. Efforts are underway to preserve the Santa Ana Sucker. The Riverside-CoronaRCD is in the process of creating an artificial stream to aid in the recoveryof the fish to the watershed.