To wine country environmentalists who have seen natural communities displaced by an ever-expanding grapescape, the notion that vineyards can be viable wildlife habitat is like calling parking lots habitat. The editors of the Monterey County Breeding Bird Atlas, while acknowledging the quality of the local chardonnays, conclude: “Few birds use these croplands; almost nothing nests in them.”
That may be too harsh a verdict. Robin Leong of the Napa Audubon Society, compiler of that county’s just-published bird atlas, says cavity-nesting birds will use nest boxes in vineyards if growers provide them. Although western bluebirds are the intended tenants, ash-throated flycatchers, tree swallows, and violet-green swallows may also move in. So, unfortunately, may starlings, attracted by leavings from the grape harvest. Other opportunistic species like crows, ravens, and blackbirds forage among the vines.
Some growers have enlisted barn owls in their rodent-control efforts. Napa resident Janet Barth, founder of Habitat for Hooters, has furnished owl boxes to a long list of growers, including prestigious names like Cakebread and Stag’s Leap. Hawk perches have also been set up to attract day-shift predators.
But intact riparian corridors provide the only real refuges for wildlife in vineyard country. Over 60 species of birds have nested in the Napa River Ecological Reserve. On a recent visit, this 73-acre enclave, hemmed in by vineyards, was alive with song. I watched newly fledged Nuttall’s woodpeckers tagging after their parents and saw a vigilant Bullock’s oriole dive-bomb a passing crow. But the Audubon atlas compilers say the reserve isn’t large enough to sustain its once-thriving population of yellow-breasted chats, which suffers from lack of genetic diversity.
Corridors are vital for mammals. To monitor traffic, wildlife biologist Jodi Hilty set up remote-triggered cameras at 21 Sonoma Valley and Alexander Valley sites where vineyards bordered riparian zones. Her project captured images of one mountain lion and numerous smaller carnivores. She found that larger predators like bobcats and coyotes frequented the wider and better-vegetated corridors, which also had a more diverse set of species. Degraded narrow corridors had higher counts of non-native predators, including feral cats and opossums.
Another recent study documented the value of riparian corridors for even smaller predators — and for growers. Researchers Clara Nicholls, Michael Parrella, and Miguel Altieri examined two organic vineyards near Hopland, in Mendocino County. The block that bordered a riparian area and was bisected by a corridor of yarrow, daisies, and other plants had lower populations of two vineyard pests, western grape leafhopper and western flower thrips, in its outer rows. Predators based in the corridor and the riparian edge, such as lacewings, ladybugs, syrphid flies, and spiders, appeared to be keeping the pests in check.
