IRVINE, CALIF. —“There’s one. Hear it?”
Biologist Paul Galvin halts to stare into the willows and mulefat scrub lining the San Diego Creek bed in Irvine.
A half-dozen birds sing, including a house finch, song sparrow and yellow-breasted chat—but Galvin waits for a strident, staccato song that resembles: Cheedle-cheedle-cheedle-chee, cheedle-cheedle-cheedle-chew.
“That’s one!” he says, lifting his binoculars toward a least Bell’s vireo.
In the past year, he’s counted 116 of these tiny birds nesting among willow groves preserved by Irvine Company.
That pleases Galvin because not that long ago, the number of least Bell’s vireo pairs seen throughout the entire United States was less than 300. And the total number seen in Orange County for two years running was this:
“Dismal” and “precariously low” was how the Atlas of Breeding Birds described the population of least Bell’s vireos in Orange County in the mid-1990s.
Vireos once thrived here. Each spring, they’d fly from Mexico and Central America to mate and raise their young along Southern California’s wooded creek beds.
In the late 1950s, however, their numbers waned. And by 1986, fewer than 300 pairs nested in the entire U.S.—prompting the U.S. Fish and Wildlife Service to declare them endangered.
Orange County bird counters saw just two vireos in 1986; one in 1987; none in 1988 or 1989; and one in 1990—a grand total of four birds over five years.
It was not until the late 1990s that their numbers began to rise again, thanks in part to Irvine Company’s efforts to permanently preserve more than 57,000 acres of open space on the Irvine Ranch, and restore habitat at more than 150 sites.
One project in particular helped bring the vireo back to a little-known creek bed.
In 1996, Irvine Company contributed 21,000 acres of open space to the Nature Reserve of Orange County.
Over the next two years, 87 vireos were counted in the county, according to Galvin, an Irvine Company consultant. One of their favorite nesting spots was along the San Diego Creek in South Orange County.
So Irvine Company began restoring 60 acres of the creek with the vireo’s favorite habitats: willow riparian forest and mulefat scrub.
Three years later, 354 vireos were counted in Orange County. Their numbers continue to rise.
For five years running, Galvin has counted about 25 nesting pairs in one restored portion of the San Diego Creek adjacent to the Los Olivos apartment community in Irvine.
Two thousand miles they fly to find this small oasis to raise their young. And it looks they’ll keep doing so.
“Our data indicate that least Bell’s vireos are now more abundant and widespread in Orange County than at any time since the late 1950s,” Galvin says. “It appears they’ve established a self-sustaining breeding population here.”
— May 2016