The threat to birds from air and water pollution, agriculture, mineral and oil extraction habitat loss and all other manner of human activity is well known to birding community members. Now to that list of threats add climate change. A recently published report by The Audubon Society’s “Birds and Climate Change Report” provides a comprehensive look at climate change’s potential impact on North American bird species, and it is not comforting. The report concluded, “Of the 588 North American bird species Audubon studied, more than half are likely to be in trouble. Our models indicate that 314 species will lose more than 50 percent of their current climatic range by 2080. Of the 314 species at risk from global warming, 126 of them are classified as climate endangered. These birds are projected to lose more than 50 percent of their current range by 2050. The other 188 species are classified as climate threatened and expected to lose more than 50 percent of their current range by 2080 if global warming continues at its current pace.”
Ornithologists have for some time suspected that warming temperatures would change the ranges of bird species whether by altering the physical character of their habitat or disrupting cycles affecting food availability.
The extent to which climate change in conjunction with human activity could severely degrade bird species viability is seen in this stark example from the Audubon report.
“The deciduous forests of West Virginia, North Carolina, and Virginia are home to several species of vulnerable warblers, notably the Cerulean Warbler. The tiny sky-blue bird, which nests high in treetops, is thought by some to be the fastest-declining songbird in North America; its winter habitat in the northern Andes has been dramatically reduced by coffee plantations, while its summer habitat in Appalachia is being steadily fragmented by, among other things, coal mining and low-density residential development. As the climate changes, the Audubon analysis shows, much of the Cerulean Warbler’s current range in the eastern United States is likely to become unsuitably wet and hot, and Appalachia’s forests will become an ever more important refuge for it and other warblers.”
That changing climate has affected bird species distribution has been known anecdotally by members of New England’s birding community for some time as we have observed a steady influx of species from other parts of the country.
One of the first I noticed was the turkey vulture. In the mid- 1990s, I first began to see these soaring scavengers over Blue Hill south of Boston. Over time their range has moved steadily northward, and they have become common throughout the Upper Valley.
Another example of a bird species coming north due to more hospitable conditions is the red-bellied woodpecker. This was a species that first appeared at the feeders of my suburban Boston home in the mid-1990s. Within the last two decades, the number of sightings at northeast bird feeders has nearly doubled from 38.3% in 1993 to 67.3% in 2013, according to Project FeederWatch (PFW). Not surprisingly, reports of red-bellieds have been on the increase in New Hampshire moving south to north. I have not had one at my feeders, but they are in the area. Just this past week a birding colleague reported a first ever one at her Kendal feeder.
Or consider the Carolina wren. PFW records show that its reported distribution at feeders in the northeast has increased nearly 50% over the last twenty years from 32.5% in 1993 to 45.2% in 2013.
Who will show up next? Black vultures, historically a bird of the south have been recorded in southern New England and are beginning to turn up in southern NH. How about the red-headed woodpecker whose range generally stays west of the Hudson River? There is one being reported in Stafford, NH, and one was sighted last year over in Vermont on Kendall Station Rd.
Of course the down side of receiving these new arrivals is that the forces bringing them here may drive away some of our native species. Studies like the Mountain Birdwatch are tracking closely the populations of potentially threatened, mountain habitat specific species like the Bicknell’s thrush and blackpoll warbler to assess whether warming climate will cause their preferred habitat to change driving them to cooler climes.
If you'd like to explore this subject further, another good resource is the recently released "The 2014 State of the Birds Report" based on research by an alliance of governmental and non-profit organizations from both the United States and Canada.