A project of

Winter Wren

The State of Winter Wrens

Regionally: Declining

A plot of Winter Wren study area abundance. The x axis show years between 2010 and 2021. The y axis shows local population size. Local population size fluctuates between roughly 1100 and 600 individuals with an overall downward trend and an especially steep drop in population between 2012 and 2015.

The mean (thick, dark red line) annual estimate of the Winter Wren abundance within the immediate areas surrounding ~750 Mountain Birdwatch sampling stations. The lighter vertical bars represent the 95% Bayesian credible interval (a measure of the uncertainty around the abundance estimates).

The numbers of Winter Wrens counted during Mountain Birdwatch surveys have been declining since at least 2012. Since 2010, the overall numbers of Winter Wren in our study area have changed by -4.12% per year (95% Bayesian credible interval = -4.85% to -3.36%). This equates to a 37% overall reduction in population size. In the both Mountain Birdwatch and the Breeding Bird Survey data sets, Winter Wren numbers fluctuate up and down frequently–these fluctuations may be related to severe winter mortality.

Although in some respects a hardy bird, as evidenced by their ability to nest successfully on mountaintops in the east or on the edge of the tundra in northern Canada, Winter Wrens are also quite sensitive to winter weather. Populations crash following severe winters in the southeastern United States, in some cases to the point of local extinction. This pattern is evident in the Mountain Birdwatch data: following the notably cold, snowy winter of 2013/2014, numbers of Winter Wren dropped dramatically.

Mean annual population trends and population change (with 95% Bayesian credible intervals [CRI]) for Winter Wren from 2010 through 2021. A red dot indicates strong evidence for a negative trend.
RegionMean annual
trend (%)
95% CRI
Probability of
Probability of
change (%)
change (95% CRI)
All regions -4.12(-4.85, -3.36)>0.99<0.01-36.92(-42.11, -31.36)
New York
-3.67(-5.10, -2.20)>0.99<0.01-33.49(-43.80, -21.69)
New York
-4.35(-7.04, -1.30)>0.99<0.01-37.84(-55.20, -13.43)
New York
-3.51(-5.04, -1.92)>0.99<0.01-32.22(-43.40, -19.16)
Vermont -3.18(-4.34, -1.92)>0.99<0.01-29.73(-38.65, -19.20)
New Hampshire -4.07(-5.08, -3.05)>0.99<0.01-36.61(-43.67, -28.88)
Maine -5.51(-6.67, -4.37)>0.99<0.01-46.29(-53.20, -38.81)

Globally: Probably stable

Data collected by the Breeding Bird Survey indicate that Winter Wren numbers across Canada and the U.S. have fluctuated significantly but show a stable overall trend since the survey began in 1966. 

State of the Mountain Birds