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Over 300 species of birds find the river a convenient stopover along the Pacific Flyway. Migrating birds stop for food and rest, and some birds are found year round, nesting and breeding. About half of the total recorded birds in Los Angeles County have even been spotted along the channelized portions of the rivers.
Shorebirds like osprey, terns, killdeer, cormorants, the California brown pelican and California least tern (both federally endangered species) who feed on fish and invertebrates are in abundance in the rivers' estuaries during April and then from July to October. Other species thriving along our rivers
include great blue herons, snowy egrets, black-crowned night-herons, red-winged blackbirds, American coots, spotted sandpipers, buffleheads, cinnamon teals, and both red-tailed and red-shouldered hawks.
Some less common species that rely heavily upon the rivers for their persistence in urban Los Angeles are: green heron, yellow warbler, lazuli bunting, loggerhead shrike, hooded merganser, western meadowlark, the endangered Least Bell’s Vireo, southern willow flycatcher and American peregrine falcon.
Many fish still thrive in the remaining soft-bottom areas of the rivers, but few are native. In Big Tujunga Wash and the Santa Clara River the federally threatened Santa Ana sucker and arroyo chub are still surviving, as is the speckled dace. Before channelization of the rivers, steelhead trout up to three feet long were common.
Reptiles & Amphibians
The upper watersheds still support thriving reptile and amphibian populations. Pacific slender salamander, pacific tree frog, western toad and dozens of species of lizards and snakes persist. The federally endangered arroyo toad and the federally threatened red-legged frog can still be found in areas along the upper Tujunga Wash, the upper Arroyo Seco and the Santa Clara River. Some of the exotic fish and other aquatic life that inhabit the rivers are crayfish and mosquito fish. These two feed on the larvae of amphibians and are thought to be responsible for the decline of newts and frogs in the river.
Just as herons and egrets prey on the crayfish, other birds feed on the insects that are drawn to the river. Blue damselflies, which are related to dragonflies, feed on smaller insects such as mosquitoes and even small fish. The males are brilliant blue, with the females gray, blue or brownish. Unlike their cousins the dragonflies, blue damselflies fly close to the surface of the water.
Butterflies and moths are drawn to both the native and non-native plants that thrive within the river ecosystem. The buckeye and western tiger swallowtail are two species of butterfly seen along the rivers.
Mammals live and forage along the rivers but most are urbanized predators such as domesticated cats, coyotes, skunks, raccoons, opossums, rats and mice. Higher up in the watershed are bobcats, coyotes, muledeer, mountain lions, American badgers, and gray foxes.