Falcons and owls and bats….oh my! Unless you are a starling, a rodent, or an insect, these winged-critters may not seem as scary as lions and tigers and bears. To starlings, rodents and insects, however, this scary trio of winged-critters represents a potentially deadly “tool” of Integrated Pest Management (IPM). The Napa Sustainable Winegrowing Group (NSWG) and the Napa County Resource Conservation District (NCRCD), in their efforts to support sustainable watershed management, have hosted several workshops with a focus on these winged critters and the benefits they can provide to agricultural communities.
On August 13, 2001, the Napa Sustainable Winegrowing Group (NSWG) hosted falconer Tom Stephans to demonstrate how falcons can be used as a tool for integrated pest management (IPM). According to Stephans, “falconry is a low-tech, non-toxic and highly effective means of pest control.” In viticulture, falcons can be used to reduce crop damage caused by non-native starlings.
“Falcons instill a deep-seated terror in starlings and other birds. As soon as a falcon is released, one can hear small birds in the surrounding trees sending out warning calls. The falcon does not need to kill the birds to get the desired result. The birds need only see the dive-bombing, swooping falcons, and they begin to scatter,” says Tom.
Female peregrines, technically called peregrine falcons, have the largest pectoral muscles of any bird its weight. It is the chest muscle that gives them power in flight. The females weigh about 2.5 pounds and have a wingspan of 3 feet. Yet in flight they can withstand 14 G’s, or 14 times the force of the acceleration due to gravity. Fighter pilots, in meek contrast, are trained to withstand 7 Gs in the cockpits of their jet planes.
Alternative methods of keeping destructive birds out of vineyards when grapes are close to being harvested include: silver streamers, netting, shooting, and devices that produce loud noises. Aside from the use of netting and the loud noise of “scare devices” (which can be very disturbing to neighbors), starlings quickly become accustomed to their surroundings and resume feeding on the fruit of the vine.
Tom owns one of only five falconry businesses in the country. He can be contacted at (760)789-1493, (760)801- 2207 or falconair4s@home.com
Owls are another “winged” critter that can be used as an IPM “tool.” NSWG and the NCRCD have promoted the distribution of barn owl boxes in vineyards for the past few years. The idea of utilizing owls to manage pests appears to be widely accepted in the Napa Valley; owl boxes can be seen in almost every vineyard.
Barn owls have been around for the last 26 million years. Because they do not have to see their prey to be successful, they are one of the most skillful rodent hunters in North America. Their dish shaped face in conjunction with their asymmetrical ears gives them the ability to triangulate on their prey like radar.
On average, a barn owl will eat 155 gophers per year. If there were 48 barn owls in an area, they would consume 7,440 gophers. A 1997-98 study in California showed that a barn owls diet consists of 42% pocket gophers, 30% voles, 17% deer mice, 6% house mice, and 5% other prey.
Installing a barn owl box provides a place for the barn owls to roost in the fall and a safe place to nest and raise a family of owlets (5-7 per box) in the spring. Annual cleaning of the box is the only maintenance involved. It is important to wear a dust mask while cleaning the box and to wash hands afterwards. Napa’s “Habitat for Hooters”(HFH) organization will build, install and clean owl boxes for a small fee that includes membership. Local high school students build HFH owl boxes and the money raised from owl box sales goes towards scholarships.
The program director of HFH is Janet Barth. She can be reached at (707)224-3464. Other barn owl contacts are Cathy Garner with the Fresno Wildlife Rescue Center at (559)298-3276 or fresnowildlife@psnw.com, and Steve Simmons from Merced High school at (209)385-6470.
Over the past two years, the NCRCD has hosted three presentations about bats and the role that they can play in IPM. Bats are also the latest IPM “tool” that NSWG is promoting for use in vineyards. UC research has confirmed that Mexican free-tailed bats and Yuma myotis bats (“little brown bats”-both very common in Napa) in Sacramento Valley prey upon night-flying insects which include serious farm and urban pests including moths, beetles, flies, midges, mosquitos and plant bugs.
Bats help keep the insect population in balance. A typical colony of 150-200 bats will eat 5 pounds of insects per night or several million insects each season. Bats may also protect crops from pests by “chasing” insects away with their echolocation calls. A number of moths, including cutworms, armyworms and bollworms, can sense bat echolocation up to 120 feet away and will turn away or dive to the ground when exposed to the pulsed sounds.
The key to the bat’s insect gathering ability is echolocation, which serves as a form of personal sonar. Their vocal squeaks, mostly above human hearing range, bounce off an insect and is picked up by their super sensitive large ears. The skin between the bat’s legs is used as a basket to scoop up the insect, the bat then does a belly tuck to lower it’s head down to eat.
Bats are the second largest mammal group in the world, roughly 950 species. All of the species found in Northern California are insect eaters that eat both flying and ground insects. However, in spite of their benefit to farms and the environment as a whole, bats have been maligned and often are subject to eradication attempts. Little effort has been made to protect the roosting and foraging habitat needed by bats. More than half of American bat species are in severe decline or are already listed as endangered, according to Merlin Tuttle, president of Bat Conservation International (BCI). In California, at least 10 of 24 species are designated “of special concern” by the California Department of Fish and Game (CDFG), meaning their numbers are in decline and they require special management to preclude further losses.
Installation of bat houses and enhancement of roost habitat are two ways to attract bats. Please note that, similar to owls and falcons, it is illegal to capture bats. For a handbook detailing bat house construction or for general information about bats, contact the Bat Conservation International at (512)327-9721 or by mail at P.O.Box 162603, Austin, TX 78716.
For additional information about the use of these “winged” critters for IPM, you can contact Astrid C. Bock-Foster with the Napa County RCD and the Napa Sustainable Winegrowing Group at (707)252-4188 or nswg@naparcd.org.