Celebration is in order for two nests of burrowing owls in Boulder County

Western burrowing owls on county open space land have successfully raised seven fledglings during the most recent nesting season, according to Boulder County Parks and Open Space, or BCOS, Senior Wildlife Biologist Susan Spaulding.

The small, underground-dwelling owls are a protected species in Colorado, and were once prevalent in prairies and grasslands throughout the state. Making their homes in abandoned prairie dog colonies and dens of species such as badgers and foxes, burrowing owls prefer wide spaces and grasslands to hunt a variety of prey.

Protections for burrowing owl territories run from March through October, according to BCOS Wildlife Biologist Michelle Durant. 

Durant, who works on the BCOS Burrowing Owl Action Committee, explained that burrowing owl males land in the seasonal territories as much as a week before a female. The protection period begins when the owls are expected to arrive in the spring, taking into account the bird’s lengthy courtship rituals, building out its burrow, nesting time with eggs and then the time to raise the fledglings.

“Burrowing owls take a long time to mature and gain proficiency to survive,” Durant said. 

The fledging time is not uncommon in raptor species in the area, Spaulding said. The county wildlife staff provide plenty of space and time for the birds to mature before winter migration, the biologists explained.

This past season, the burrowing owls chose to build their nests on agricultural land leased by the county. Durant said the specific areas were kept intentionally discreet to keep onlookers from crowding the fragile birds.

“They’ve nested all over the eastern and southern parts of Boulder County and not just in the same place every year,” Durant explained. “If there is a prairie dog colony, it's fair game.”

Seven is a low number for the population, the biologist added. Nearby regions have reported nests with more than ten fledgling owls, numbers Durant would like to see in Boulder County’s population. 

“Three (owls) at one nest and four at the other is our local average but it’s not great,” Durant said. “It’s not sustainable.”

The exact cause of the low reproduction numbers is a source of speculation for the scientists. The low numbers could be attributed to survival rates from predators. Because the birds dwell underground, they can be targeted by local critters like foxes, weasels and badgers, Spaulding said. 

When owls show up on BCOS properties, a lot of work goes into giving the small predator birds time to grow safely. This is especially true when that nesting site is someplace more complicated, Spaulding explained, like land leased to agricultural tenants. Biologists like Spaulding and Durant work closely with county agricultural staff and the tenants farming on the land to ensure that the owls have a safe habitat that won’t disrupt the agricultural work as well.

To help protect the burrowing owls and other species in Boulder County’s wild spaces, Durant encouraged visitors to keep their dogs on leash, stay on designated trails and keep an eye on signs that indicate critical wildlife habitats.