Bringing back bluebirds
Insects make up more than two-thirds of a bluebird's diet.
The western bluebird is an insectivore, with more than two-thirds of its diet coming from insects.
A cherry grower in The Dalles, Oregon, is putting new focus on his integrated pest management practices to bring a more natural and balanced ecosystem into the orchard.
Mike Omeg is shifting his insecticide program from what he describes as a "scorched earth" approach to one using softer materials and doing things to encourage biodiversity in the orchards, such as installing nesting boxes and raptor perches to attract insect- and rodent-eating birds, bats, and owls. "We want to encourage more bluebirds and tree swallows and implement practices that will foster more of them," he said during an orchard tour held last fall to look at the Omegs' nesting boxes and perches for birds, bats, and raptors.
In the past, they used aerial applications of malathion in their pest management program. While the material is not toxic to wildlife, he said it is toxic to quite a few insects, such as flies and bees. "I want to encourage more native bees in the orchard for their pollination services and also allow more food for the bluebirds and tree swallows."
But at the same time, he has to manage Western cherry fruit fly. "All of us know that we can't mess around with that pest. We absolutely have to control it without any risk of failure involved."
He believes the time is right to transition to using GF-120, a bait formulation of spinosad insecticide that has developed a following in Washington State for inexpensively and safely controlling cherry fruit fly. Research has proven the treatment effective, Omeg said, adding that he is shifting to GF-120 as a way to leave other food (insects) in the orchard for birds and bats.
"No product that is labeled in our crops will kill adult codling moths," he said. "They're bulletproof. We can only kill the worms." He wants to have birds and bats eliminating codling moth and obliquebanded leafroller adults, preventing thousands of eggs from being laid, instead of playing catch up with insecticides.
Bluebirds and tree swallows are insectivores, with more than two-thirds of their diet coming from insects. During the fall and winter, when insects become scarcer, they will feed on small fruits and seeds.
Bluebirds eat more ground insects, while tree swallows prefer flying insects, and are expert at catching insects in the air, according to John Schuster of Wild Wing Company, a bird conservation consulting business located in Cotati, California. Bluebirds are not migratory, although tree swallows are.
Three species of bluebirds are native to North America—the eastern, western, and mountain.
When the nation's first European settlers arrived from England, eastern bluebirds were abundant. It has been reported that early colonists built wooden nesting boxes and placed them around their farms to encourage bluebirds to help control their insect populations.
However, bluebird populations declined after introduction in the 1800s of the house sparrow and European starling, both aggressive species that overtook the bluebirds' nesting cavities. Loss of habitat added to the birds' decline.
Schuster recommends that bluebird nesting boxes be spaced at least 100 yards apart, because bluebirds are territorial. Nesting boxes should always face east, he said, explaining that bluebirds are diurnal and hunt most aggressively when they leave the box in the early morning hours. East-facing placement helps the birds find the box faster because of the sun shining on a contrasting dark hole. He adds that bluebirds and tree swallow boxes can be paired together.
The nesting hole size for bluebirds should be 1-9/16 inches in diameter; for tree swallows, 1-3/8 inches. The proper size hole will prevent starlings from getting inside the box. Using steel posts will eliminate cats and other mammals from climbing poles to get to the nests. He suggests that a diamond pattern be followed when placing nesting boxes in the orchard.
Placing the houses low, about 4.5 feet off the ground, acts as a passive house sparrow control to keep sparrows from taking over the nest, he said.
"All you have to do to take care of your box is to clean it out twice a year," Schuster said, noting that bluebirds have two clutches annually. Cleaning it out after the fledglings have left is important to encourage the building of another nest. The nest should be broken up and scattered in other areas of the orchard.
"Never throw the nesting material on the ground at the base of the box," he said. "If you do, you're ringing the dinner bell for the raccoons and others that will take advantage of the scent that attracts them to the box."
Bluebird nests are distinguishable by their beautifully shaped bowls, while swallows have bowls that are lined with feathers, Schuster said. "The nest of a house sparrow will be a hodgepodge mess, with string, yarn, garden debris, and other trash."
After the box has been cleaned, the bluebirds will be back in two weeks to nest again, Schuster said. "By cleaning the box out twice a year, you'll get two sets of fledglings and twice the benefit of the insect-eating that takes place from the bluebirds."