My bluebird season started March 31, as I hiked around Como Park's golf course in St. Paul, making sure all the sturdy cedar nest boxes were firmly mounted on their poles and ready for occupancy after the long winter.

The season ended 4 1/2 months later, in the second week of August, when I cleaned out the last bedraggled clump of nesting material from one of the 15 boxes that make up my bluebird trail.

In between lay a summer of encouraging these beautiful blue thrushes to set up housekeeping. I walked the trail each week to check that weather and predators were being kept out, made minor repairs and booted out house sparrows whenever they took up residence.

Success doesn't always come easily on my trail, with sparrows and occasional vandalism causing some nests to fail. But a total of 35 young bluebirds flew out of their nest structures and joined their parents in the big wide world over the summer. And the nearby bluebird trail within Como Park produced 42 young bluebirds, for a total of 77 for the park as a whole.

Many Minnesotans volunteer as bluebird trail monitors each year. In 2009, more than 500 volunteers in the official Minnesota Bluebird Recovery Program reported nearly 21,000 new bluebirds emerging from nest boxes statewide.

"And that's probably just the tip of the iceberg," says Carrol Henderson, who directs the Department of Natural Resources' Nongame Wildlife Program. "There easily could have been 100,000 to 150,000 new bluebirds fledged in 2009," as many people set up and monitor nest boxes but don't get around to filling out data forms.

Whatever the number, it's a vast improvement from 50 years ago, when a bluebird sighting was rare. Loss of trees and fenceposts offering nesting cavities, competition for nest sites from sparrows and starlings, and the widespread use of pesticides delivered a triple whammy to this charismatic species.

Some passionate individuals set out in the 1970s to change things, forming bluebird societies and encouraging volunteers to put up nest boxes and monitor trails. The DNR's Nongame Program held workshops, and Henderson produced an excellent book, "Woodworking for Wildlife, Homes for Birds and Animals." The recent third edition spells out everything you need to know to be a good bluebird host.

Bluebird FAQs

• Won't bluebirds abandon their nests if their box is opened each week to check for signs of trouble? The answer is no; the birds are momentarily disturbed but quickly fly back in to tend eggs or nestlings.

• How do other birds know that the nest boxes are intended for bluebirds? They don't: Various species of birds such as tree swallows, wrens and chickadees frequently adopt bluebird houses, and that's just fine with us monitors. The one bird we won't tolerate is the house sparrow, since this non-native species attacks and even kills bluebirds to take over a box. (Sparrows are one reason why the small thrush's numbers plummeted in the past century.)

• Why place the nest boxes on a golf course? It turns out that golf courses (and cemeteries) offer ideal habitat for bluebirds -- open areas with short grass that allow the birds to easily hunt ground-scuttling beetles and other insects.

As I walk in Como Park in early fall I can often hear the soft, melodious song of a bluebird family talking to each other. Golfers are treated to the sight of bluebirds flitting from ground to nest box to feed the youngsters.

Yes, bluebirds have come back from a time when their numbers were dangerously low. It's much more likely these days that you'll spot a flash of brilliant blue as the birds with a big fan club continue to bound back from the brink.

Val Cunningham, a St. Paul nature writer, bird surveyor and field trip leader, can be reached at