The State of Winter Wrens
Regionally: Stable, for the moment, following a sharp decline
The mean (thick, dark 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 thinner, lighter lines represent less probable estimates of the annual abundance.
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 -2.70% per year (80% Bayesian credible interval = -4.50% to -0.85%). This equates to a ~30% overall reduction in population size over the last 14 years. In the both Mountain Birdwatch and the North American 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 Northeast 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 80% Bayesian credible intervals [CRI]) for Winter Wren from 2010 through 2023. A red dot
indicates strong evidence for a negative trend. Strong evidence is suggested for a trend when the 80% CRI does not contain zero.
| Region | Mean annual trend (%) | Trend 80% CRI | Probability of decrease | Probability of increase | Population change (%) 2010-2023 | Population change (80% CRI) |
|---|---|---|---|---|---|---|
| All regions | -2.70 | (-4.50, -0.85) | 0.96 | 0.04 | -29.90 | (-45.05, -10.45) |
| New York (Catskills) | -3.05 | (-5.12, -0.99) | 0.97 | 0.03 | -33.14 | (-49.53, -12.08) |
| New York (Adirondacks) | -2.58 | (-4.41, -0.67) | 0.95 | 0.05 | -28.85 | (-44.39, -8.36) |
| Vermont | -2.47 | (-4.31, -0.54) | 0.95 | 0.05 | -27.75 | (-43.63, -6.82) |
| New Hampshire | -2.67 | (-4.51, -0.79) | 0.96 | 0.04 | -29.70 | (-45.08, -9.81) |
| Maine | -2.85 | (-4.71, -0.90) | 0.96 | 0.04 | -31.33 | (-46.58, -11.11) |
Globally: Slightly declining or stable
Data collected by the North American Breeding Bird Survey indicate that Winter Wren numbers across Canada and the U.S. have fluctuated substantially but show a slightly declining overall trend since the survey began in 1966. eBird trends show much more regional variation, but estimate that Winter Wrens have declined by as much as 10% to 40% over the last decade in New England and Eastern Canada.
