From the Santa Cruz Weekly:
With its bright blue back and rust-colored chest, it’s easy to see why the western bluebird is a frequent birder’s favorite. Soon viticulturists may number among its fans as well.
According to the research Dr. Julie Jedlicka conducted as part of her doctoral thesis at UC–Santa Cruz, the western bluebird may serve as a natural alternative to insecticides to manage some of the pests that invade California’s vineyards. Jedlicka found that placing nesting boxes on vineyard plots lures in populations of the entirely insectivorous bird, which in turn can fend off insect-borne blights such as the deadly Pierce’s disease.
After placing pieces of what she calls “highly energetic yummy pieces of bluebird food” on plots both with and without nesting boxes, Jedlicka found that 2.4 times more insects vanished (presumably because they were eaten) from the plots containing nesting boxes, probably due to the fact that sites containing nesting boxes saw a tenfold increase in bluebirds sightings.
For more, see: UCSC Grad Finds Bluebird–Wine Connection