Greg surveyed the situation and built a bat house of his own design, to provide a more attractive alternative to our little friends. He mounted the house in the winery eaves. And it worked… sort of. The bats moved in and began multiplying and eventually overpopulated the house. Two years later, in 1997, Greg built a second bat house to accommodate the increased population and attached it close to the first bat house. And it worked… sort of. The bats moved in there and overpopulated that house, too. This only became evident during periods of extreme heat. To escape the congested habitat and extreme heat generated inside the house on those afternoons, large quantities of both infant and adult bats would move to the outside of the box and cling on to the outer surface as much as possible. It was very disturbing to witness the infants that would fall to the ground unable to navigate to escape the heat. Efforts to return them to their bat house would prove unsuccessful. In the winter of 1998, the houses were removed from the side of the winery and mounted back-to-back on steel poles partially shaded by Eucalyptus trees to provide a cooler site with better air flow. And it worked… sort of. The number of bats inhabiting these houses was estimated at between 600 & 900 at one point. Occasionally during the summer months, Cindy & I would have friends up to the winery right around sunset. We would set up aluminum chairs and sip wine while waiting for the bats to exit for their evening of feeding. First, one or two would come out followed by maybe 3 or 4 more. And then it was like the order was given to vacate the premises. Over the next minute, the bats poured out of the holes in continuous ribbons. It was very exciting to witness one of nature’s finest moments.
One summer period of extreme heat occurred so early in the day, that the houses were still in the full sun. I was saddened by yet another significant die back, mostly of infants. That winter, we relocated both houses, still on the poles, to the interior section of an old Oak tree by one of our vineyard blocks. This was to provide shade at all times of the day. And it worked… period.
So, we are landlords to two different types of bats; The Mexican Free-tailed bat and the Pallid bat.
I read with interest a recent article (By ROBERT DIGITALE) in the Santa Rosa Press Democrat about bats. Patricia Winters, president of the Forestville-based California Bat Conservation Fund gave a presentation to grape growers and pest workers on the value of bats in insect management.
The following excerpts are from that Press Democrat article.
RE: The Mexican Free-tailed bats
"She's a little bat," said Winters, known to Bay Area schoolchildren as the Bat Lady. "But she can fly faster than any other bat in the world. And she can fly up to two miles high, and all she eats are crop pests."
Winters showed graphics from Doppler radar and thermal imaging to depict billions of moths moving north from Mexico into southeast Texas at a height of almost two miles. Each night the moths run into what Winters called the largest concentration of mammals on the planet, an estimated 200 million Mexican free-tailed bats living in caves outside Austin and San Antonio.
Only 2 percent of the moths ever make it past the bats, which can fly at speeds of 60 mph, Winters said. One recent study estimated that the bats prevent about $1 billion a year in U.S. crop damage.
RE: Other bats
Winters told the group that a lactating Big Brown female bat, a species found in Sonoma County, can eat twice its weight in insects each night.
Kathy Cowan, who volunteers with Winters, said she has a standard argument for convincing women about the value of bats. She focuses on the work the animals do in pollinating tropical fruit and reseeding rain forests.
"If we didn't have bats," Cowan said, "we wouldn't have chocolate."
Click here for the entire article and to see a great picture of a Pallid Bat: