OCEANSIDE, Calif. – Alex Fromer, a biologist for RECON Environmental, Inc., walked over to a crew getting ready to spray invasive plants alongside the San Luis Rey River on May 17 and discussed the precautions they should take while in the vicinity of least Bell’s vireo nests.
“There are a few active least Bell’s vireo nests in the area,” Fromer said, “and we need to ensure the crews maintain a proper distance to ensure the nests remain active and healthy.”
The crews were required to take the precautions because of an environmental window that either forbids any type of construction activities or requires that specific protective measures be taken. Along the San Luis Rey River, located in northern San Diego County adjacent to Camp Pendleton, the environmental window extends from mid-March to mid-September. One of its primary beneficiaries is the least Bell’s vireo nesting season.
Fromer and two crews, one to spray invasive plants and another to water newly planted native vegetation, are in the river basin as part of an ongoing effort to restore the environment for native plants and animals while maintaining flood risk reduction measures for the homes, business and infrastructure that line the river.
Tom Keeney, a biologist for the U.S. Army Corps of Engineers Los Angeles District, said the work is part of carefully planned management effort along the final 7.2 miles of the river.
“The plan includes 58,000 new native plants and has to be very precise,” Keeney said.
Part of the precision is how to re-establish a more representative natural environment and still maintain the river’s flood risk reduction measures of managing a 71,200 cubic feet per second flow rate.
“We need to maintain a balance between providing flood risk management and maintaining a viable vireo habitat,” Keeney said. “We’ll plant black willow, sandbar willow and arroyo willow, Freemont cottonwood, mulefat and native herbaceous plants.”
Herbaceous plants can best be described as annual plants, those that re-grow each year and never become woody.
“It’s important to maintain natural vegetation, especially for sensitive species like the least Bell’s vireo,” Fromer said. “Habitat loss has been a main factor for why their numbers were decreasing. The natural habitat will help not only the vireo, but every other native species in area.”
“As with all natural systems, it varies from year to year,” Fromer said about the number of nesting vireos. “There had generally been a decline with vireo numbers, but now we’re starting to see an increase, and we’re hoping active restoration will bring numbers back up to historic highs.”