The mountain bluebird (Sialia currucoides) is a small thrush found in open woodlands and meadows in western North America. With its brilliant blue plumage and melodious song, this species has captivated nature enthusiasts for generations. However, due to habitat loss and competition from other bird species, mountain bluebird populations have declined significantly over the past century. This has led many to wonder – just how rare is the mountain bluebird today?
In this article, we will explore the current status and distribution of the mountain bluebird. We will look at population trends and the major threats facing this species. We will also examine what is being done to help protect and restore mountain bluebird habitats across western North America. Gaining a better understanding of the rarity and conservation needs of the mountain bluebird will be key to ensuring this iconic species continues lighting up our skies for generations to come.
Current Population and Distribution
The mountain bluebird is a member of the thrush family Turdidae, which includes other popular songbirds like the American robin and Eastern bluebird. Within the genus Sialia, the mountain bluebird is most closely related to the Western bluebird and Eastern bluebird. There are estimated to be about 1.5 million mountain bluebirds across their range today.
The breeding range of the mountain bluebird extends from Alaska through western Canada and the western United States. Their range reaches as far south as New Mexico and Arizona. They winter primarily in the southern parts of their breeding range, migrating only short distances compared to many other passerines.
Within their breeding range, mountain bluebirds occupy open coniferous forests, burned or cleared woodlands, ponderosa pine savannas, and mountain meadows. They can be found at elevations up to 12,000 feet in the summer months. Prime mountain bluebird habitat contains a mix of scattered trees, snags, and fence posts for perching and nesting, with open ground for foraging on insects.
Population Trends
After experiencing significant population declines in the early 1900s, mountain bluebird numbers rebounded during the mid-century. From 1966-2015, North American Breeding Bird Survey data indicates mountain bluebird populations increased by an average of 0.05% per year. However, in recent decades,numbers have been declining in certain portions of their range, such as the southern Rockies.
Overall, Partners in Flight estimates the global breeding population at 1.5 million, with 78% spending part of the year in the United States, and 22% in Canada. The species is ranked as a species of Least Concern by the IUCN Red List due to its relatively large and widespread population. However, local declines and habitat pressures still pose concerns for the long-term outlook of this species.
Threats and Conservation Concerns
The major threats facing mountain bluebirds today include:
– Habitat loss due to human development, logging, and fire suppression. Mountain bluebirds rely on open coniferous forests and burns, which have declined.
– Competition with other cavity nesters for nest sites. The non-native European starling and house sparrow often outcompete bluebirds for nesting cavities.
– Climate change. Shifting precipitation patterns and high summer temperatures may affect prey insect populations and stress breeding birds.
– Predation. Nest predation by squirrels, chipmunks, snakes, and other species can limit reproductive success.
To help conserve mountain bluebird populations, public agencies and non-profit groups have implemented initiatives such as:
– Nestbox programs to provide additional cavities for breeding and reduce competition. Over 23,000 nest boxes have been installed in bluebird habitat.
– Prescribed burning and forest thinning to improve nesting and foraging habitat conditions.
– Removal of invasive nest competitors like starlings and house sparrows.
– Protection of high-quality breeding areas through parks, reserves, and other designations.
– Monitoring and research to track populations and better understand conservation needs. The Western Bluebird Monitoring Network coordinates surveys across the west.
– Outreach campaigns to educate the public and build support for conservation. BLUEInk for Bluebirds promotes “neighbor to neighbor” protection.
Geographic Distribution
While mountain bluebirds remain relatively widespread across western North America, their distribution is uneven and populations in certain areas are declining. Here is an overview of mountain bluebird distribution and trends within different parts of their range:
Pacific Northwest
The mountain bluebird is a year-round resident west of the Cascades in Oregon and Washington. Breeding populations are concentrated at higher elevations in the Cascades, Olympic Mountains, and northern Rocky Mountains. The Puget Trough and Willamette Valley also support populations where open oak savannas provide habitat. Trend data indicates mountain bluebird numbers have been stable or increasing in recent decades in Washington but declining in Oregon.
California
In California, mountain bluebirds breed in the Sierra Nevada, Cascade, Klamath, and coastal mountain ranges. The highest densities occur in the southern Sierra Nevada with an estimated population of 250,000. While still common, declines have been noted in the central and southern Sierra. Coastal populations have also declined, especially in central California.
Intermountain West
The Intermountain West represents the stronghold for mountain bluebird populations, where extensive high-elevation coniferous forest provides prime habitat. All states including Idaho, Montana, Wyoming, Nevada, Utah, Colorado, and New Mexico host breeding populations of 100,000+ birds. Trend data shows mixed regional patterns, with increases noted in Montana but declines in Colorado, Wyoming, and other areas.
Southwestern U.S.
In the Southwest, mountain bluebirds reach the southern limits of their range in Arizona and New Mexico. Breeding birds are found at higher elevations including the Mogollon Rim, White Mountains, and Sacramento Mountains. The total population in this region likely numbers fewer than 50,000 birds. Ongoing declines have been detected on survey routes in Arizona.
Western Canada
Canada supports approximately 22% of the global mountain bluebird population, primarily in British Columbia and Alberta. Breeding populations extend through the Coast Mountains, Columbia Mountains, Canadian Rockies, and central British Columbia plateaus. The highest densities occur from south-central BC to west-central Alberta. Breeding Bird Survey data suggest mountain bluebird populations have been stable or increasing in most of western Canada over the past 40 years.
Region | Population Estimate | Population Trend |
---|---|---|
Pacific Northwest | 150,000 | Stable/Increasing |
California | 500,000 | Declining |
Intermountain West | 1,000,000 | Mixed |
Southwestern U.S. | 50,000 | Declining |
Western Canada | 300,000 | Stable/Increasing |
Rarity Within Range
While mountain bluebirds remain fairly common and widespread across their breeding range as a whole, they face localized rarity issues in portions of their range. Here is a look at regions and habitats where the mountain bluebird has become quite rare:
Coastal California
In coastal central and southern California, the mountain bluebird has declined significantly over the past century due to habitat loss. For example, the species essentially disappeared as a breeding bird in the San Francisco Bay Area prior to 1970. Targeted nest box efforts have helped to reestablish small populations, but the species is still extremely limited in coastal areas from San Francisco to Los Angeles.
Southern Rocky Mountains
Parts of the Rocky Mountains in Colorado, Wyoming, and New Mexico have also seen worrying population declines. For example, in the Front Range of Colorado the mountain bluebird is now designated as a Species of Greatest Conservation Need. Causes likely include forest maturation, fire suppression, and competition with other cavity nesters.
Lower Elevations
While mountain bluebirds reach their highest densities at mid to high elevations, small populations historically occupied lower elevation ponderosa pine and oak savanna in some areas. These low elevation habitats have declined severely across the west, making the bluebirds reliant on high elevation sites.
Northern Range Periphery
On the northern edge of their range in British Columbia, Yukon, and Alaska, mountain bluebirds occur more sporadically at lower densities. For example, they are considered uncommon breeders across much of central Yukon. Loss of lower elevation breeding habitats has increased their rarity in these peripheral northern regions.
Significance of Local Rarity
The increasing rarity of the mountain bluebird in certain areas should be a cause for concern even if overall populations remain relatively robust. There are several reasons why local rarity matters for the conservation of this species:
Genetic Diversity
Small isolated populations lose genetic diversity over time through inbreeding and random mutations. This can reduce fitness and adaptability. Protecting habitat connectivity between populations helps maintain genetic exchange.
Resilience
When populations decline to low levels over large portions of their range, it makes them more vulnerable to extinction risk from threats like disease, predators, or changing conditions. Distributed robust local populations provide insurance against localized extinction events.
Ecosystem Roles
As a cavity nesting insectivore, the disappearance of the mountain bluebird can impact community dynamics and ecosystems. Nest cavities they produce are used by other birds and mammals over time. Declines in insectivores can also disrupt food chains.
Cultural Value
The mountain bluebird holds special cultural significance to many Indigenous peoples as well as nature enthusiasts across the west. Local rarity reduces opportunities to experience this beloved songbird and blue flash of color in the wild.
In summary, monitoring and addressing localized rarity of the mountain bluebird will be critical for maintaining viable populations, genetic health, ecosystem functions, and cultural connections to this species across its range into the future. Robust local populations will provide the foundation for long-term conservation success.
Efforts to Track and Conserve Rare Populations
Several monitoring and conservation initiatives are underway specifically aimed at rare and declining mountain bluebird populations:
California Monitoring
The Western Bluebird Recovery Program monitors California populations and manages nestbox trails to support small coastal populations. Annual surveys identify population hotspots and gaps needing habitat restoration.
Colorado Reintroductions
The Colorado Bluebird Project has worked to reestablish mountain bluebird nesting pockets along the Front Range through releases of birds raised in captivity. Paired with nestboxes and habitat management, these efforts have helped boost local numbers.
Southern Rockies Surveys
The Southern Rockies Bluebird Project coordinates volunteer monitoring for bluebird populations across high-elevation habitats in Colorado and New Mexico. The effort has documented declines and evaluated limiting factors.
Oregon Habitat Initiatives
The Prescott Bluebird Recovery Project works to improve habitat on public and private lands in central Oregon, a priority area after severe regional declines. Their efforts combine tree thinning, prescribed fire, and nestbox placement.
Idaho Genetic Research
A University of Idaho study investigated genetic diversity and population structure to identify unique or isolated mountain bluebird populations in need of protection in the state. They recommend maintaining habitat corridors.
Targeted research and localized management will be key to restoring balance in rare pockets across the range of the mountain bluebird. With appropriate conservation action guided by monitoring, even small populations can be nurtured back to become part of thriving regional metapopulations.
Conclusion
The mountain bluebird remains a common and vibrant species across large swaths of western North America thanks to adaptable habitat needs and an affinity for human-created openings. However, the species faces challenges from habitat loss, competitors, and other factors leading to population declines in portions of its range. Areas and habitats where the mountain bluebird has become quite rare should be priorities for continued monitoring, research, and management efforts. Maintaining distributed robust local populations will strengthen the overall health and resilience of this species. With strategic conservation investments, the scenic sight and comforting song of the mountain bluebird will continue brightening high-elevation landscapes for generations to come.