SNAP*Shot: Mountain Bluebirds

Hello friend! It was a wonderful trip spending time with Sandhill Cranes this March. However, there was another site I know you’ll enjoy as much as I did. What a surprise to spend time with a flock of Mountain Bluebirds (Sialia currucoides). You cannot miss them hunting in the grasses. They clearly do not blend in.

I’m always surprised to see Mountain Bluebirds in valleys and plains, but it should be no surprise. Why? Their winter habitats are at lower elevations in grasslands, deserts, and agricultural areas with a few trees and in pinyon-juniper tree areas. During breeding season some bluebirds stay in these sagebrush flats and lowland prairies, but many nest across the mountain west at elevations up to 14,000 feet, although more common at 11,000 feet. Now that’s high.

Here in the large San Luis Valley we sit at about 7,700 foot elevation. Not what most people would consider a low elevation, but the farmland and types of trees are attractive to Mountain Bluebirds. Besides, if they want to nest higher they don’t have to go far. The mountains surrounding San Luis Valley are some of the highest in Colorado including 14,000+ foot peaks.

Today we saw no females. They may have been in the larger flock quite a ways from the road, but they also more easily blend into the landscape so we may have missed them. Female Mountain Bluebirds are mostly gray/brown with some pale blue on wings and tail. You can still see a bit of the gray/brown on this juvenile male. As with most birds, initially the young are the same “blending-in” color as the female.

The birds on the grasses in the field are hunting. Their diet is primarily insects of all kinds but during breeding season their favorites are beetles, grasshoppers, and especially caterpillars. They also catch insects on the fly and can hover above their potential prey much like a Kestrel. They also eat berries, especially in winter, and can be found feasting in the berry-laden junipers.

Bluebirds are cavity nesters, but today many Mountain Bluebirds breed in human-made nest boxes. Much of what we know about them comes from studies focused on nesting-box birds. Data that has been collected on natural preferences include using old Woodpecker holes, holes in dirt banks, crevices in cliffs or among rocks, and holes in sides of buildings. No wonder they like the nests designed specifically for them in open spaces with scattered trees and low scrubs often with nest guards to protect the eggs and young from marauders and bad weather. Sounds like a great and safe home in their preferred wilderness. Interested in building a bluebird nest box? Check this out.

Mountain Bluebirds arrive earlier to breeding grounds than their cavity-nesting rivals. The male finds his nest of choice and guards it fiercely. As the females arrive the courting male will fly back and forth between the nest cavity and the perched female. The female in turn will decide on a mate not based on his song, his flight, or how beautifully blue he is. Rather her choice is based on the quality of the nest cavity. Once the female makes her choice, her complete attention goes to building the nest inside the crevice or box.

So what is it like for Mountain Bluebirds to raise a family? Once the female completes building the nest, she will lay between 4 and 8 eggs. She alone incubates the eggs between 13 and 17 days. The male feeds the female while she is incubating and both parents feed the unfeathered helpless young. The young leave the nest about 17 to 23 days after hatching. Both parents tend to the young for another 3 to 4 weeks. Then they often have a second brood. That is a pretty intense summer schedule if you ask me. BUT, keep up the good work! Bluebird numbers are stable even with the usual loss of habitat problem. They may just find more crevices in buildings.

As breeding season winds down, flocks of 30 or more Mountain Bluebirds begin to form. Each flock forms around one or more families with dependent fledglings. As the last fledglings become independent, adult birds who did not produce this year may join the flock. These flocks may leave the area for days or weeks, returning to visit their nesting grounds for a few hours or days, until eventually they disappear from the area. They may migrate to other parts of their range or simple move to better wintering grounds close by. Mountain Bluebirds are in San Luis Valley all year long. It may be the winter home to migrating flocks from further north as well as those that like staying here all year.

So, here’s looking at you kid, but I need to find the prize-winning cavity for this year’s family-to-be.

Find the bluebirds where you live, whether Eastern, Western, or Mountain. They actually don’t mind people, so sit down and be enchanted. Until next time my friend . . .