Least Bell’s Vireo Now Confirmed at Freshwater Marsh & Riparian Corridor

Least Bell's Vireo. Image (c) 2010 and courtesy of River Partners (http://www.riverpartners.org/index.html)

The Friends are delighted to announce that a state and federally endangered species, the Least Bell’s Vireo (LBV), has been confirmed nesting at two different places in our neighborhood: the Riparian Corridor at Playa Vista, and just adjacent to the 25-acre Freshwater Marsh at the corner of Lincoln and Jefferson, in a part of the Ballona Wetlands Ecological Reserve run by the California Department of Fish and Game. Both the Riparian Corridor and the Freshwater Marsh were built by Playa Vista under a 1990 agreement with the Friends of Ballona Wetlands, which ensured these 51 acres of habitat were constructed, and will be maintained in perpetuity by the Playa Vista community.

The Least Bell’s Vireo nesting (and foraging at the Freshwater Marsh) is GIGANTIC news because, while occasional transient individuals have been observed since 2003, there are no historic records of nesting in the Ballona Valley. These vireos (one of four subspecies of Bell’s Vireo; the other three are not endangered) prefer a habitat of riparian (streamside) vegetation at low elevations, with year-round freshwater, so they may have been here prior to the 1800s when that habitat was common in the Ballona Valley. After that time, the area was drained for farming, livestock grazing, and other uses, significantly altering the habitat.

1908 Postcard of strawberry fields at Lincoln and Jefferson Boulevards (site of present day Freshwater Marsh). Postcard courtesy Duke Dukesherer

Other Los Angeles County populations of Least Bell’s Vireos are located along Santa Clara River, Big Tujunga Wash (Hansen Dam), Los Angeles River (Sepulveda Basin), San Gabriel River, and Rio Hondo (Whittier Narrows), and the bird formerly occurred throughout the L.A. Basin.

According to a colored leg band observed on the nesting female LBV in the Freshwater Marsh, she traveled north to find a home. The band indicates that she was tagged as a juvenile in 2008 at Camp Pendleton (near San Clemente), where there are larger LBV populations.

The primary cause of the endangered status for the LBV is loss of habitat. The LBV is also victimized by cowbirds (a native species that lays its eggs in another bird’s nest), which could be a contributing factor. Control of cowbirds at large nesting areas such as Prado Basin and Camp Pendleton, and the immediate recovery of vireo populations there, has indicated this is the case.

The Freshwater Marsh and Riparian Corridor are under the management of the biologist Dr. Edith Read, who is also a member of the board of the Friends of Ballona Wetlands. The Freshwater Marsh opened in 2003.

Listen to the Least Bell’s Vireo here.

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