The State of Blackpoll Warblers
Northeastern United States: Rapid decline
Mountain Birdwatch data indicate a steep overall population decline (-5.1% per year, 95% credible interval = -6.0% to -4.2%) in the mountains of our region; this trend equates to a 34.2% decline (95% credible interval = 28.8% to 39.1%) between 2011 and 2019. The steepest declines were observed in Maine (see table below). These declines are in broad agreement with the USGS Breeding Bird Survey annual trend estimate (-5.8%) for our region.Mean annual population trends (below) for Blackpoll Warbler from 2011 through 2019. A red dot indicates strong evidence for a negative trend. A trend of -2%, for example, indicates that the number of Blackpoll Warblers in our study area has declined by an average of 2% each year from 2011 through 2019.
|Region||Mean annual trend (%)||95% credible interval|
|All regions combined||-5.1||(-6.01, -4.15)|
|New York (state)||-4.19||(-5.62, -2.72)|
|New York (Catskills)||-5.70||(-7.39, -3.84)|
|New York (Adirondacks)||-3.59||(-5.42, -1.73)|
|New Hampshire||-4.23||(-5.41, -3.01)|
Globally: Likely declining
Overall, Blackpoll Warbler appears to have been declining in numbers for many decades. Data collected by the USGS Breeding Bird Survey indicate large declines (>5% per year) in the number of Blackpoll Warblers counted across Canada (where most of the population lives), especially between 1970 and 1990. 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.
Opportunities for Conservation
Scientists have not studied Blackpoll Warblers sufficiently to understand where and how to target conservation interventions, and we do not know why their populations are likely declining so rapidly. By attaching miniature light-level geolocators to adult Blackpoll Warblers from Alaska to Vermont, we now have good documentation of their spectacular migration routes. We do not, however, understand where the limiting factors occur during the annual cycle of this species. Has fledgling production on the breeding grounds declined? Is their long migration a particularly hazardous life period? Is deforestation and habitat degradation on the wintering grounds driving these declines? 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.
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 U.S. Indeed, 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.