State of the Mountain Birds — 2025
Most northeastern mountain bird species have declined since 2010
years of monitoring
mountain stations
monitored species
Fifteen years of monitoring by hundreds of community scientists reveal substantial population changes among birds breeding in the high-elevation spruce–fir forests of the northeastern United States. Mountain Birdwatch surveys nearly 800 long-term sampling stations across Maine, New Hampshire, Vermont, and the Adirondack and Catskill Mountains of New York.
Our analyses indicate that many characteristic mountain bird species—including Blackpoll Warbler, Bicknell’s Thrush, Hermit Thrush, Swainson’s Thrush, White-throated Sparrow, Winter Wren, and Yellow-bellied Flycatcher—have declined since monitoring began in 2010. Across these species, populations have decreased by an average of roughly 40% during the monitoring period.
Declines are particularly pronounced in the Catskill Mountains, the southernmost portion of the northeastern spruce-fir ecosystem. Within our Catskill monitoring network, several species have declined by more than half since 2010.
Climate change is likely a major factor shaping these patterns. As temperatures warm, spruce-fir forests are expected to contract and shift upslope, reducing suitable habitat for species adapted to cold, high-elevation environments.
Overall population change for the ten Mountain Birdwatch bird species and Red Squirrel between 2010 and 2025 across the northeastern United States. Values represent the estimated cumulative percent population change since monitoring began. Negative values indicate population declines relative to 2010, while positive values indicate increases. Error bars represent 95% credible intervals from hierarchical community N-mixture models.
● decline with strong evidence
● uncertain trend
● increase with strong evidence
Regional population trends for Mountain Birdwatch species from 2010–2025. Colors indicate the estimated annual rate of population change for each species within five monitoring regions. Red shades indicate declines, while blue shades indicate increases. Gray cells represent regions outside a species’ primary breeding range.
Northeast United States population trends
The table below summarizes overall population trends estimated from the Mountain Birdwatch monitoring program. Trends represent the estimated mean annual population change since 2010 and the cumulative change over the monitoring period. Colored symbols indicate the direction and strength of evidence for population change.
| Species | Annual trend (%) | Trend (95% CRI) | Probability of increase | Population change (%) 2010-2025 | Population change (95% CRI) |
|---|---|---|---|---|---|
| Yellow-bellied Flycatcher | ●-1.02 | (-1.65, -0.37) | <0.01 | -14.1 | (-22.1, -5.4) |
| Black-capped Chickadee | ●1.55 | (0.46, 2.71) | >0.99 | 26.3 | (7.1, 49.3) |
| Boreal Chickadee | ●4.76 | (3.19, 6.35) | >0.99 | 102.1 | (60.2, 151.8) |
| Winter Wren | ●-2.50 | (-2.96, -2.04) | <0.01 | -31.6 | (-36.3, -26.6) |
| Bicknell's Thrush | ●-3.80 | (-4.57, -3.05) | <0.01 | -44.1 | (-50.4, -37.2) |
| Swainson's Thrush | ●-2.22 | (-2.58, -1.85) | <0.01 | -28.6 | (-32.5, -24.4) |
| Hermit Thrush | ●-6.38 | (-7.39, -5.31) | <0.01 | -62.7 | (-68.4, -55.9) |
| Blackpoll Warbler | ●-4.00 | (-4.45, -3.54) | <0.01 | -45.8 | (-49.5, -41.8) |
| White-throated Sparrow | ●-4.70 | (-5.14, -4.25) | <0.01 | -51.4 | (-54.7, -47.8) |
| Fox Sparrow | ●1.48 | (-0.33, 3.36) | >0.99 | 25.7 | (-4.8, 64.1) |
| Red Squirrel | ●9.24 | (8.28, 10.24) | >0.99 | 277.4 | (229.6, 331.4) |
● strong decline
● weak decline
● weak increase
● strong increase
What these results mean
Together, these results suggest that many species associated with high-elevation spruce-fir forests are experiencing sustained population declines across the Northeast. Declines are especially pronounced in southern portions of the monitoring region, consistent with expectations that climate change will affect southern and lower-elevation populations first.
Mountain Birdwatch provides one of the only monitoring programs capable of tracking population change for these species across remote high-elevation habitats. Continued long-term monitoring will be essential for understanding how mountain ecosystems respond to ongoing environmental change.
Explore the results
Detailed results for each species—including regional trends, population change estimates, and figures—are available on the individual species pages linked in the navigation menu above.
A downloadable PDF summary of the 2025 report and a complete table of population trend estimates are available in the sidebar.
