Are Mountain Bluebird populations declining?
Yes, most long-term datasets show Mountain Bluebird population declines, especially in parts of Southern Alberta. But are population numbers truly changing - or are we just getting better at noticing them?
It sounds like a simple question, but the answer is anything but. Across western North America, researchers and citizen scientists are examining the data to find out. From long-running bird surveys to modern tools like eBird and NestWatch, a clearer picture is starting to emerge.
That picture is mixed by region. Some areas show steep declines while others look stable. Local monitoring remains essential.
There are still gaps and uncertainty in the data, so let’s take a closer look at the evidence and the questions that matter most right now.
Mountain Bluebirds investigate an MBTCS nest box - one of many simple steps you can take to support monitoring efforts that help us better understand population trends.
What do the numbers tell us?
Since 1970, the United States and Canada have lost about 2.9 billion breeding birds, and many losses involve common species. Mountain Bluebirds are part of this broader story and are showing steep population declines.
“Unlike the other bluebird species, which have increased over time, the Canadian population of Mountain Bluebird has experienced a large decline of 60% since 1970 according to the Breeding Bird Survey.” NatureCounts - The State of Canada's Birds
Across Canada, bird trends differ by species and region
Birds that live in Canada’s grasslands have declined by 67% since 1970.
Birds Canada and Environment and Climate Change Canada. 2024. The State of Canada’s Birds Report. Accessed from NatureCounts.
Scientists have tracked bird populations using large-scale surveys like the North American Breeding Bird Survey (BBS) and citizen science platforms like eBird. These datasets power national assessments like Birds Canada’s NatureCounts and The State of Canada's Birds report.
These programs are among the largest continually growing datasets supporting scientific research. They help us see big trends across regions and over time in a way that we have never been able to achieve before, but interpreting those trends is where the challenge begins.
Dr. John Sauer of the U.S. Geological Survey has analyzed BBS data and estimates that Mountain Bluebird numbers have declined by about 20% since 1970, a slow but steady drop averaging 1.5% per year. That’s roughly one million birds fewer than half a century ago.
But newer data from eBird tell a different story - one that’s potentially more urgent. Tom Auer, a spatial data scientist at the Cornell Lab of Ornithology, examined 15 years of eBird checklists and identified a possible 34% decline between 2007 and 2021 across the species’ breeding range.
The consistency between eBird and BBS lends credibility, but it also raises a bigger question: Is this a sudden drop, or just a clearer view of a longer-term trend?
Are we simply seeing the result of improved monitoring and participation? And how confident can we be in these estimates?
These are exactly the kinds of questions being asked by leading scientists working to understand the status of Mountain Bluebirds.
Watch NABS’ Current Status of the Mountain Bluebird:
To explore these findings in more depth, we recommend watching the excellent overview presented at the North American Bluebird Society (NABS) conference on October 29, 2022. The virtual session, titled "Current Status of the Mountain Bluebird," brought together four leading experts:
Dr. John Sauer (USGS) – presented long-term trend data from the Breeding Bird Survey
Tom Auer (Cornell Lab of Ornithology) – shared recent eBird-driven models and spatial analyses
Robyn Bailey (NestWatch) – explored data from thousands of monitored bluebird nests
Dr. Brooke Bateman (Audubon) – explained climate risk projections and future range shifts
Together, their presentations provide a well-rounded and up-to-date look at what the numbers are telling us, and what they’re still not.
Data from BBS and eBird show regional population changes over time - your backyard observations help validate these trends and are easier than ever to contribute with programs like eBird and NestWatch!
What is driving the decline of Mountain Bluebird populations?
Scientists point to interacting factors rather than a single cause:
Habitat loss and change
Where native grassland and sage habitats remain intact or are restored, bluebirds tend to do better; conversion and invasive grasses can depress numbers. Researchers have linked population health to native habitat.Insect availability
Bernie Daniel has pointed to another pressing concern: are there enough insects to feed bluebird chicks? Some nest box monitors report nestlings dying close to fledging, possibly from insect shortages. But how widespread is this? Are newer pesticides like neonicotinoids playing a role? And what about changes in insect timing due to warmer springs?Climate stressors
Climate projections from Audubon’s Dr. Brooke Bateman suggest Mountain Bluebirds are highly vulnerable to future warming. If global temperatures rise by 3°C, more than half of their current summer range may become unsuitable. Are we already seeing the effects? Will they shift northward into Alberta?Extreme weather
Late snowstorms. Spring cold snaps. Drought. Heat waves. These kinds of events can devastate nesting attempts or reduce adult survival. But which ones matter most? And are they becoming more frequent in key breeding areas?
These questions point directly to what we should be watching, counting and recording here on the ground.
Why Southern Alberta matters to Mountain Bluebirds
Mountain Bluebird breeding season abundance map on eBird confirms Southern Alberta as a notable breeding area.
eBird trends maps show a patchwork with some Southern Alberta 27-km cells in decline, others not statistically different from zero, and some increasing.
Southern Alberta faces real-world pressures that significantly affect cavity-nesters like Mountain Bluebirds:
According to Multisar, only about 26% of Alberta’s native prairie remains in relatively natural condition, and what’s left is fragmented. The State of Canada’s Birds report from Birds Canada indicates that the single biggest threat to Canada’s grassland birds is the destruction and degradation of the native grasslands they need. Urgent action to conserve their habitat is needed to save these species.
Southern Alberta continues to track long-term drought conditions and water-shortage advisories. Historic water-sharing agreements in the southern basins were necessary in 2024 and advisories continue into 2025. Such conditions affect insect availability and bluebird nesting success.
Together, this means Southern Alberta is both significant for Mountain Bluebirds and sensitive to changes.
Are nest boxes helping Mountain Bluebirds?
Yes, nest boxes have long been one of the most successful grassroots conservation tools. They give bluebirds a place to nest when cavity nesting sites are scarce. But the where and how matter.
Since the 1970s, MBTCS has field-tested and refined nest box design and placement in southern Alberta. Lessons from decades of monitoring shaped practical standards like entrance size and height, interior dimensions, ventilation, roof overhang, predator guards, spacing and wind orientation.
Leverage 50 years of MBTCS field experience and shared knowledge, build your own nest box with our proven Mountain Bluebird nest box plans, designed for southern Alberta.
Thanks to programs like MBTCS and NestWatch, we now have thousands of bluebird nesting records, and that number grows every season. Robyn Bailey, who leads NestWatch, has helped turn those reports into real insights, but the full picture is still forming. For instance, Trail Monitors of the future will help answer questions like:
Why is egg failure the leading cause of nest loss?
Do predator guards actually improve outcomes?
Are Tree Swallows or House Wrens displacing bluebirds more often now than before?
Citizen scientists are helping answer these questions. But to get reliable results, we need consistent reporting, especially from under-monitored regions like Southern Alberta.
REMINDER TO MBTCS MEMBERS: Trail Monitors are asked to submit Annual Report forms by September 1 so results can be compiled for year end reporting
Dedicated MBTCS volunteers help maintain over 2,700 nest boxes across southern Alberta. Together, we gather the evidence needed to better understand Mountain Bluebird populations.
What’s missing from the data?
Researchers still need a full population model for Mountain Bluebirds, one that combines nest success, adult survival, migration patterns and wintering behaviour. Right now, there are still gaps in the data, especially in rural and northern regions.
To understand Mountain Bluebird population dynamics, we need to know:
Which part of the lifecycle (adult survival, chick survival, or productivity) limits populations most?
Where do nest boxes yield the biggest gains today and why?
How do heat waves, cold snaps, drought, and poor insect timing change results each year? What simple nest-box changes (for example: more vents, shade, bigger roofs, light paint, insulation, and strong predator guards) make boxes safer for bluebirds here in southern Alberta?
Where is monitoring too thin to resolve local trends, and how can we close those gaps?
Answering these requires both professional research and data from local nest monitors like you.
Have you reported your nest box data yet?
What can you do to help?
Rather than assuming we have the full story, perhaps the best approach is to lean into curiosity. Ask more. Share more. Collaborate more. As you clean out boxes or reflect on the season’s notes, here are 5 ways to stay involved:
Join Climate Watch surveys to monitor winter and breeding season patterns
Observe and report trends in chick health, predator pressure, or insect abundance and record first arrival and last departure dates
Each dot on this NestWatch map represents a monitored Mountain Bluebird nest, providing real-time data contributed by citizen scientists across North America. These records not only support research on population trends, but also help local monitors compare, learn and contribute to a larger conservation effort that impacts all birds.
Mountain Bluebird populations are changing - and the data shows it
If Mountain Bluebirds are indeed declining, we can’t afford to wait to act.
The most important thing we can do for Mountain Bluebird conservation right now is to track better data and contribute our part to the larger community.
Whether you manage 100 nest boxes or just spot a few birds each year, your observations help shape the bigger picture.
As we think towards the next season, the question isn’t just “Are Mountain Bluebirds declining?”, it’s “What can we learn if we keep watching?”
Share your thoughts and observations in the comments below.
