As spring starts to slowly creep back into Colorado, many species also come back to the state for the warmer months. Once temperatures begin to increase, Coloradans will notice more monarchs, hummingbirds, and bluebirds fluttering around.

According to the Estes Valley Watershed Coalition, many bluebirds will be choosing their nesting sites in places around Northern Colorado throughout the next few weeks. Mountain Bluebirds usually arrive in the mountains of Colorado in late February to early March and the Western Bluebirds tend to arrive a bit later. They are such an important species for Colorado to see come back each year, as the overall population of these colorful birds is significantly dwindling.

The Audubon Society of Greater Denver explains a couple of reasons why Mountain, Western, and Eastern bluebirds are becoming less common in Colorado. The primary causes of the population dip are habitat loss and increased competition for nesting sites. Bluebirds are second cavity nesters, which means they aren't capable of making their own homes. Instead, they conveniently move into nests that have already been previously established by other birds or also into holes in trees.

Several cities across the Centennial State, including Estes Park and Castle Rock, have also taken increased efforts to help conserve bluebirds. The Colorado Bluebird Project is an official plan in which residents and towns install artificial nesting boxes where bluebirds can make safely construct their nests in. These boxes imitate the tree cavities that these birds typically live in. People with existing boxes should make sure they are cleaned out and cleared of debris, as the birds return for the season.

Anyone can install an artificial nest box in their yard or on their property to help sustain the bluebird population in Colorado.

RELATED: What is the Colorado Bluebird Project?

Amazing Wildlife Viewing At Colorado Drive-Thru Refuge

The Rocky Mountain Arsenal National Wildlife Refuge actually isn't all that new, but there are plenty of folks in Colorado who are yet to make the discovery. With more than 15,000 acres of land, it's one of the largest urban wildlife refuges in the country.