The State of Winter Wrens
Regionally: Stable, for the moment, following a sharp decline
The mean (thick, dark brown line) annual estimate of Winter Wren abundance—calculated as the annual sum of estimated Winter Wren within the local area (a 4-hectare circle) surrounding all 791 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 -3.07% per year (95% Bayesian credible interval = -3.74% to -2.34%). This equates to a ~31% 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 2022. A red dot
indicates strong evidence for a negative trend. Strong evidence is suggested for a trend when the probability of population increase or decrease (from 2010 to 2022) equals or exceeds 95%.
| Region | Mean annual trend (%) | Trend 95% CRI | Probability of decrease | Probability of increase | Population change (%) 2010-2021 | Population change (95% CRI) |
|---|---|---|---|---|---|---|
| All regions | -3.07 | (-3.74, -2.34) | >0.99 | <0.01 | -31.19 | (-36.74, -24.76) |
| New York (state) | -3.37 | (-4.70, -1.98) | >0.99 | <0.01 | -33.72 | (-43.86, -21.36) |
| New York (Catskills) | -5.53 | (-7.79, -2.94) | >0.99 | <0.01 | -49.45 | (-62.24, -30.12) |
| New York (Adirondacks) | -2.85 | (-4.27, -1.36) | >0.99 | <0.01 | -29.32 | (-40.79, -15.20) |
| Vermont | -2.36 | (-3.49, -1.15) | >0.99 | <0.01 | -24.90 | (-34.73, -12.92) |
| New Hampshire | -2.31 | (-3.18, -1.41) | >0.99 | <0.01 | -24.44 | (-32.13, -15.67) |
| Maine | -4.56 | (-5.67, -3.41) | >0.99 | <0.01 | -42.89 | (-50.35, -34.07) |
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.
