Monitoring nest boxes offers insights in local bluebird population

Every spring, both mountain and western bluebirds return to Western Montana, delighting residents and nature lovers alike. 

But where they spend their winters remains largely unknown. 

“I’ve had some of the ones I’ve banded show up in California, but there really isn’t a strong tracking system for where our bluebirds overwinter,” Jane Brockway shared during a recent talk at the Mineral County Library. “We’re lucky to have both species here. Mountain Bluebirds usually thrive above 5,000 feet, and while Superior sits at just 2,725 feet, both species make this area their home.”

If an organization includes the word "bluebird," the odds are Brockway is involved. She's been passionate about these birds since 1998. Now retired from her career as a registered nurse, she dedicates her time to studying and sharing the lives of these vibrant migratory birds.

Each spring, Brockway monitors around 100 bluebird nest boxes. Every week, she checks for eggs, chicks, and bands young birds — all while fending off invasive starlings. 

“That’s why the size of the box is so important,” she explained. “Starlings will move in if they can, but the correctly sized hole keeps them out.”

According to Brockway, an ideal bluebird box should be about 10 inches tall, with a 5-by-5-inch floor, made of 3/4-inch thick wood. For the two species in Montana, the entrance hole should be 1 9/16 inches in diameter — slightly larger than what's required for eastern bluebirds. And absolutely no perch on the front of the box.

She and her husband, Alan, designed a chalet-style roof that is pointed and extends further over the front. 

“It prevents magpies and crows from perching on top and grabbing the bluebirds as they exit the box,” she said. These specially designed boxes are deployed in areas with high populations of ravens and magpies. “Turkey vultures hang around, but they only eat carrion, so they’re not a threat.”

Brockway says the 2017 Sunrise Forest Fire provided powerful lessons about bluebird adaptability. At the Mineral County Airport, she watched three resilient pairs nest successfully in boxes amid daily activity from firefighting crews and aircraft. 

“They had roped off one of the nest boxes on a gatepost. Trucks, helicopters, you name it, but those babies still fledged. I was so proud.” 

She did help by taking mealworms to each box, every day, but still credits the bluebird parents. She maintains about 20 boxes around the airport and many more throughout the area.

“Missoula and Mineral counties are unique because both species coexist here,” she said. “Some years we see more mountain bluebirds, other years more westerns. Sadly, I haven’t had any mountain bluebirds on my trails the past two years.”

One behavior that often surprises people is how fledglings from a first brood help feed the chicks from a second. 

Pointing to a photo of bluebirds on a fence, she explained, “These are all young birds. The male’s by the box, the female is inside with a new clutch, and those fledglings on the barbed wire fence are helping feed their younger siblings.”

She also showed a photo of a nesting site in a railroad tie on their ranch, originally excavated by a woodpecker. 

“It’s important to leave dead trees or anything that can form cavities as they’re potential nesting sites. If you need to cut down a tree, do it in late fall. You never know what’s living inside during nesting season.” 

That same railroad tie, she noted, also houses a Flicker family at its base. 

“It’s not the best post, but it’ll stay there for as long as it lasts.”

Discussing the ecological impact of wildfires, Brockway said, “As destructive as fires are, they benefit cavity nesters long-term. Within a couple of years, the burnt trees are full of insects. Woodpeckers move in first, and other birds follow.” 

Ponderosa pine trees are especially attractive to western bluebirds due to their abundance of spiders, a key dietary staple.

She works alongside a few other local monitors, while the central data collector for Montana resides near Wolf Point. Brockway spends two full days each week checking her boxes, from the first empty nest to hatching, banding, and fledging. If a second clutch is laid, the process begins again. At the end of summer, she and Alan clean out each box to prepare for the next season.

As of the week of May 10, she had counted 50 to 60 eggs, with over 30 chicks already hatched. 

“Those early ones are usually from older, more experienced birds, and they’re the ones who often produce a second brood.” 

Right now, the young birds are busy consuming insects for protein and largely ignoring seeds or fruits.

Brockway welcomes anyone interested to join her on her bluebird box route to witness the process firsthand. She can be reached at janebrockway@blackfoot.net.