The State of Black-capped Chickadees
Most of us probably don’t think of Black-capped Chickadees as a montane species, but this species readily adapts to human-modified landscapes–including mountain summits. For example, this species can be found in high densities within the spruce-fir forest around the upper parking lot near the top of Mt. Mansfield in Vermont. Mountain Birdwatch data suggest that Black-capped Chickadee numbers have increased at an annual rate of 4.55% (95% Bayesian credible interval = 1.78% to 7.44%) in the spruce-fir mountain zone of the northeastern United States since 2010. Black-capped Chickadees were not counted during the first iteration of Mountain Birdwatch (from 2000-2009), so whether recent increases reflect a long-term trend is unclear. However, in 2010 Black-capped Chickadees were absent from the six Mountain Birdwatch routes in the Catskills. Our models estimate that there are now likely >20 Black-capped Chickadees around the sampling stations along these six routes in 2022, despite no obvious changes to the forest composition. While this growth is impressive, there are two points to keep in mind. 1) Black-capped Chickadees are still very rare in the spruce-fir zone along Mountain Birdwatch routes, so their trends are disproportionately affected by the addition or subtraction of a few individuals each year. 2) Black-capped Chickadees certainly breed in the spruce-fir zone at low densities, and they nest atop Mt. Mansfield, but the figure above suggests that Black-capped Chickadees may be erratic into this forest biome in some years. Boreal Chickadees, for example, are also known to be erratic from year-to-year: they may be locally common one year, and entirely absent the next–perhaps related to local food availability and abundance.Mean annual population trends and population change (with 95% Bayesian credible intervals [CRI]) for Black-capped Chickadee from 2010 through 2022. A blue dot indicates weak evidence for a positive trend, while a purple dot indicates strong evidence for a positive trend. Strong evidence is suggested for a trend when the probability of population increase or decrease (from 2010 to 2022) equals or exceeds 95%; conversely, weak evidence is suggested for trends where the probability of change is <95%.
change (95% CRI)
|All regions||4.55||(1.78, 7.44)||<0.01||>0.99||70.56||(23.57, 136.56)|
|4.54||(0.20, 9.59)||0.02||0.98||70.36||(2.44, 200.00)|
|3.49||(-2.30, 11.08)||0.13||0.87||50.96||(-24.32, 252.96)|
|5.19||(0.34, 11.44)||0.01||0.99||83.47||(4.16, 266.67)|
|Vermont||5.82||(1.43, 10.55)||<0.01||>0.99||97.06||(18.52, 233.33)|
|New Hampshire||4.41||(1.15, 7.86)||<0.01||>0.99||67.92||(14.71, 147.83)|
|Maine||3.93||(0.28, 7.57)||0.02||0.98||58.82||(3.45, 140.02)|
Data from the North American Breeding Bird Survey indicate the Black-capped Chickadee numbers are overall increasing across the United States and Canada (~0.5% per year). These increases, however, are largely confined to the upper Midwest and the eastern half of the species’ range; Black-capped Chickadees trends are negative in the lower Midwest and much of the western US and Canada.