Mountain Bluebird Guide (Sialia currucoides)

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I was on a hike in the Coconino Nation Forrest in Flagstaff, Arizona, when suddenly, I saw a quick dash of vibrant blue feathers dart through the sky. I knew it wasn’t a Blue Jay, and it looked different than the Eastern Bluebird I’m accustomed to seeing. I used my Audobon identification app to narrow down my sighting based on color, size, and habitat. A quick scroll through eight matching results, and I had my answer! It was an adorable Mountain Bluebird. I spent the rest of the afternoon learning more about this small but stunning bird so I could be prepared for the rest of my hikes throughout the mountains of the western United States.


The Mountain Bluebird belongs to the order Passeriformes, passer meaning “sparrow” and formis meaning “shaped.” This order contains 6,500 bird species and is reserved for songbirds and perching birds with three forward-pointing and one backward-pointing toe. This specific toe arrangement allows for optimal perching.

Family Turdidae encompasses small to medium-sized thrushes. Thrushes are plump, ground-feeding birds that are often inhabitants of wooded areas—the Mountain Bluebird’s genus, Sialia, groups North American bluebirds of the thrush family. Other bluebirds included in this genus are the Western Bluebird and the Eastern Bluebird.

Mountain Bluebird

How to Identify a Mountain Bluebird

When identifying birds, it is essential to keep these four key features in mind:

  • Size and Shape
  • Color Pattern
  • Behavior
  • Habitat

In situations where you can only catch one or two identification keys, the free Audobon identification app works wonders at helping you narrow down your sighting.

Size, Shape, and Color Pattern

The Mountain Bluebird is a small thrush that’s size falls between a sparrow and robin. They are six to seven inches long with a wingspan of eleven to fourteen inches. On average, the Mountain Bluebird weighs about one ounce or thirty grams. The bills of both sexes are a dark graphite color, short and pointed. Males have a decadent sky blue coloration with a light powder blue chest fading into white underparts below the wings. The male’s wing tips and tail feathers richen into a royal blue gradient.

Females are less flashy and harder to sight, but still magnificent creatures. They are gray-brown throughout their upper parts, with their chest fading from gray to a creamy white color below their wings. Females will have blue tinges throughout their wings, tails, and sometimes along the nape of the neck. Their tailfeathers may also have dark gray tips blending with the blue features. They have a small white ring around their eyes. During the fall, females sometimes display a bit of orange-brown on their chest.

Juveniles appear in a soft grey color and will look similar to females. Juvenile males will display a deeper blue and sometimes light brown calico plumage as they mature. They will not have spots on their back like other species of juvenile bluebirds.


Now that we’ve covered size, shape, and color pattern, let’s delve into the behavior of the Mountain Bluebird. These birds are relatively accustomed to humans and will nest in backyards within their distribution range (more on that in the below habitat section).

When foraging, you will notice that Mountain Bluebirds maintain a hover. They will pounce on insect prey from a perched elevated position. They are a migratory species, traveling in flocks during the winter. Search for them along power lines and fence posts in suburban areas.

During breeding seasons, watch out for territorial Mountain Bluebirds that will dive at humans and other threats. They will snap their bills as a warning for you to give them some distance.


The Mountain Bluebird has two songs. At dawn, listen closely for a loud chirruping song often mistaken for the robin. Other times, they will sing a gentle warbling for several minutes. Their calls are a less melodic “tew” and elevated clicking “tink” when they alert others of nearby danger.

Where Does a Mountain Bluebird Live: Habitat

We’ve already learned so much about this unique bird, but where can you find one? Mountain Bluebirds prefer wide-open spaces (to the tune of The Chicks) and woodlands across western North America. Living year-round in California, Nevada, Utah, Arizona, Colorado, and Utah, your chances of spotting one are high!

From early spring to summer and often into early fall, they will be in middle to higher elevations. In high elevation forests, they are commonly spotted in large clearings. During winter, they seek out lower elevations, berry-rich junipers, pinyon woodlands, plains, and grasslands.

As a quick reference, you can find the Mountain Bluebird in the following biomes and climates:

  • Tundras
  • Mountainous Grasslands and Shrublands
  • Coniferous Forests
  • Grasslands and Farmlands
  • Temperate
  • Aird
  • Cold
  • Polar


The Mountain Bluebird is the most migratory bluebird. In late fall and early spring, migration towards lower elevation areas begins in large flocks of 20 to 200. These large flocks can include other species of bluebirds, juncos, and sparrows. They can be found in most southwest states extending to central Mexico. In the summer, they can be located as far north as Alaska.

Attracting Mountain Bluebirds

If you are within their distribution range, try your luck at attracting these beauties to your backyard. You will need to have a generally open space for them to consider your yard an excellent habitat. Place nesting boxes away from buildings and in open rural areas before the breeding season (April to September). Low shrubs and scattered tree clumps are ideal, while any densely wooded areas will fail to attract Mountain Bluebirds.

It would be best to hang boxes in pairs 100 yards apart and 10-20 feet between pairs. Perching locations within 100 feet of the box will improve your chances. Mount a predator guard on the bird box to hinder nest raiders. Plant junipers and introduce a moving water feature to entice them further.

Mountain Bluebird Diet and Feeding

Mountain Bluebirds are omnivores with excellent foraging skills. Their diet is insect-heavy during breeding and warm summer months, usually consisting of beetles, crickets, spiders, ants, bees, and caterpillars. They will forage for seeds, berries, and fruits when winter approaches. Popular berry choices include juniper, mistletoe, and hackberry.

This thrush feeds on the ground, similar to the Wood Thrush or Varied Thrush. But they hover low to the ground more than other bluebirds. When hovering, the Mountain Bluebird will pounce on prey like a falcon. When perched, they will dart out to catch prey quickly.

Mountain Bluebird Breeding

The Mountain Bluebird is a monogamous bird that forms a bonded pair. When it comes time to breed, from April to September, the males will make their way to the breeding grounds to select a nesting site. The females will arrive shortly after. Courtship behavior is then displayed in efforts to attract a mate. The male will fly around his nesting site while performing his mating call at sunrise. After mating occurs, a female who couldn’t pass up the male’s prime real estate will begin the nest-building process.

Mountain Bluebird Nesting

Mountain Bluebirds are known to use old woodpecker holes, birdhouses, and dry cavities three feet from the ground. Nesting sites along cliffs and buildings are not uncommon.

Get this funny fact! Males will mimic the act of bringing nesting materials to the cavity, but they aren’t actually carrying anything. With some birds, we see a joint effort between the male and female to build the nest, but the male’s mimicking behavior is a downright slap in the feathers to that hardworking female.

The female will then focus on actually gathering nesting materials. She will spend early mornings collecting grass stems, twigs, and pine needles and then build the base structure of the nest, usually about two inches in diameter. She will make it in the furthest corner from the cavities entrance.

Nesting cavities are chosen with openings that face away from any potentially stormy weather (ok, so the males contribute something). The female will switch gears from collecting coarse materials and focus on gathering soft plant materials like fine grasses and barks to line the nest’s interior, which is about two inches deep. A bonded pair will reuse nesting cavities during and outside of breeding season.

Where breeding ranges overlap, the Mountain Bluebird has been known to mate with the Eastern Bluebird and Western Bluebird. There are no recognized subspecies at this time.

Mountain Bluebird Eggs

Female Mountain Bluebirds will lay a clutch size of four to eight eggs, laying one egg per day for several days. Eggs are pale blue with no other markings. The female then spends her time incubating the eggs over the next 13 to 17 days while the male focuses on bringing ample food to the female to reduce her time away from the nest. Nestlings typically hatch throughout the same day but sometimes hatch one day later. Both mom and dad will feed and protect the naked and helpless chicks, but the male supplies a more considerable amount of food in the early days after hatching. Nestlings weig

Once the Mountain Bluebird nestlings reach 17 to 23 days old, it is time for them to fledge. The young are still dependent on their parents post-fledging anywhere from three weeks to two months. On average, two broods are produced per season.

Mountain Bluebird Population

From 1966 to 2015, the North American Breeding Bird Survey estimated there had been a 24% decline in the Mountain Bluebird population. The estimated global breeding population, according to Partners in Flight, is 4.6 million.

Partners in Flight also estimates that 80% of Mountain Bluebirds spend most o the year in the United States, while 20% breed in Canada and 31% spend winters in Mexico.

mountain bluebird sitting on the tree brunch

Is Mountain Bluebird Endangered?

The Mountain Bluebird is not endangered. Oddly enough, the species benefited from the growth of logging and grazing industries during the nineteenth and twentieth centuries—clearing densely wooded spaces meant for easier foraging and more habitat opportunities. Conversely, forest and agriculture industries have created a shortage of nesting locations. Trees are too small to offer suitable cavities, and competition for sites has increased. The Mountain Bluebird cannot excavate these sites on its own and must rely on other birds like the woodpecker for help.

Conservation Efforts

Eliminating the use of pesticides will positively impact many bird species, including the Mountain Bluebird. Insecticides such as DDT leave behind residues that affect eggs. Organochlorines inhibit thick shells from forming, leading to unsuccessful nesting efforts.

Efforts to grow the population include the intentional placement of nesting boxes. While the Mountain Bluebird must compete with Western Bluebirds, Sparrows, Starlings, and Wrens for these sites, their numbers have still increased.

Conservationists need more information on Mountain Bluebirds’ habits to strategize their efforts successfully.

Mountain Bluebird Predators

Predators of the Mountain Bluebird are primarily other birds with a few nest raiders to recognize. Cooper’s hawks, peregrine falcons, great-horned owls, and cats threaten adult and juvenile Mountain Bluebirds. Nest raiders looking to snack on an egg or nestling include raccoons, weasels, rodents, and tree snakes. Nest raiders looking to snack on an egg or nestling include raccoons, weasels, rodents, and tree snakes.

They will attempt to defend themselves by diving at their foe. Humans are no exception. If you encounter a Mountain Bluebird snapping its bill at you, this is a warning sign that you are in their bubble and need to back off.

Mountain Bluebird Lifespan

A lifespan of six to ten years is most likely for a Mountain Bluebird that has passed the juvenile phase. Common to most birds, mortality rates among the species are highest during the first year of life.


Question: How rare is the Mountain Bluebird?

Answer: Mountain Bluebirds are somewhat rare to see. When considering North America’s other bluebirds, their population numbers seem low. For reference, there are 23 million Eastern Bluebirds and 6.7 million Western Bluebirds. If you live within the Mountain Bluebird’s distribution range west of the Rocky Mountains, you are likely to see one of 4.6 million Mountain Bluebirds.

Questions: Where do Mountain Bluebirds live?

Answer: Mountain Bluebirds live in mid to high-elevation areas across western North America. They prefer open space in mountainous regions, grasslands, pastures, and alpine meadows. They will become inhabitants of rural backyards with low shrubbery and ample unobstructed space.

Question: What is the difference between a bluebird and a Mountain Bluebird?

Answer: Mountain Bluebirds are a sky blue color with a powder blue throat and chest. Their wings and tailfeather fade into a deep blue. Other bluebirds, such as the Eastern and Western Bluebird, has prominent orange-brown plumage on their chests. Other bluebirds will also have gray bellies.

Research Citations

Wiggins, D. (2006). Mountain Bluebird (Sialia currucoides): A Technical Conservation Assessment. Retrieved from

Johnson, L. S. and R. D. Dawson (2020). Mountain Bluebird (Sialia currucoides), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Mountain Bluebird. (2014, November 13). Retrieved June 30, 2022, from Audubon website:

Mountain Bluebird. (2021, May 7). Retrieved June 28, 2022, from AZ Animals website:

Mountain Bluebird – Sialia currucoides – NatureWorks. (n.d.). Retrieved June 28, 2022, from website:

Sibley, D. (2016). Sibley birds. West: field guide to birds of western North America (p. 344). New York: Alfred A. Knopf.

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