The State of Blackpoll Warblers
Regionally: Rapid decline
The mean (thick, dark brown line) annual estimate of Blackpoll Warbler abundance—calculated as the annual sum of estimated Blackpoll Warbler 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).
Mountain Birdwatch data indicate a steep overall population decline (-4.56% per year, 95% credible interval = -5.23% to -3.90%) in the mountains of our region; this trend equates to a 42.91% decline (95% credible interval = 47.54% to 37.97%) between 2010 and 2022. The steepest declines were observed in Catskills (see table below).
Mean annual population trends and population change (with 95% Bayesian credible intervals [CRI]) for Blackpoll Warbler from 2010 through 2022. A red dot
indicates strong evidence for a population decline. 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 | -4.56 | (-5.23, -3.90) | >0.99 | <0.01 | -42.91 | (-47.54, -37.97) |
| New York (state) | -4.60 | (-5.96, -3.09) | >0.99 | <0.01 | -43.19 | (-52.19, -31.39) |
| New York (Catskills) | -7.24 | (-9.33, -4.73) | >0.99 | <0.01 | -59.41 | (-69.15, -44.08) |
| New York (Adirondacks) | -3.59 | (-5.19, -1.82) | >0.99 | <0.01 | -35.50 | (-47.22, -19.83) |
| Vermont | -3.73 | (-4.86, -2.52) | >0.99 | <0.01 | -36.61 | (-45.02, -26.39) |
| New Hampshire | -4.83 | (-5.73, -3.92) | >0.99 | <0.01 | -44.81 | (-50.75, -38.09) |
| Maine | -4.85 | (-5.97, -3.78) | >0.99 | <0.01 | -44.94 | (-52.20, -37.04) |
Mountain Birdwatch is the only monitoring program that rigorously tracks Blackpoll Warbler populations, and it will likely play a crucial role in our understanding of this species in the northeastern United States. Blackpoll Warbler’s preference for high-elevation breeding habitat in the northeastern U.S. clearly put this species long-term existence at risk from global climate change. Under most climate change scenarios, Blackpoll Warbler ranges are predicted to move steadily northward and to disappear from New England by the end of this century. Recent research (manuscript in prep) by Jason Hill suggests that Blackpoll Warbler are already responding to climate change, and that their populations in the northeastern U.S. have significantly tracked upslope by more than 50 m from 2011 to 2019. Clearly, more research is needed, and quickly, to identify effective conservation and management strategies for this species.
Globally: Declining
Overall, Blackpoll Warbler appears to have been declining in numbers for many decades resulting in a ~70% decline in population across North America in the last half century. Data collected by the USGS Breeding Bird Survey indicate large declines (~2.7% per year since 1970 and even steeper declines of -3.4% per year since 2009) in the number of Blackpoll Warblers counted across Canada (where most of the population lives). Declines appear to be steepest in the eastern portion of the range. This species is very difficult to monitor in Canada, however, because its core breeding habitat is so remote and inaccessible. As such, confidence in these estimates is low.
