Dave Mehlman, the director of The Nature Conservancy’s migratory bird program, is blogging all week about the new “State of the Birds 2010″ report, of which he is a co-author. Read all his posts on the report — then go to my.nature.org to learn more about the report and the Conservancy’s work to protect birds.
The 2010 State of the Birds report focuses on birds and climate change — and found that birds of the three primary terrestrial habitat types (aridlands, grasslands, forests) showed relatively the least vulnerability to global warming.
However, each of these habitat types contains species that are dramatically more vulnerable to climate change. Even more notable, most of these species are not currently considered of conservation concern, suggesting that future attention will be warranted if action is not taken now.
Aridlands and grasslands share similar predicted effects of climate change: They will become warmer and drier. In aridlands, we also expect the already variable precipitation regime to become yet more variable, with longer and harder droughts and infrequent spells of heavy precipitation.
Aridlands are also at risk of increased invasion by non-native species of plants which could have major negative effects on our native avifauna. Examples of vulnerable aridlands species are found across the country, including Greater and Gunnison Sage-Grouse of the Colorado Plateau and Great Basin, Bendire’s and Crissal Thrasher of the Chihuahuan Desert, Black-capped Vireo of the Edwards Plateau, and Wrentit of the coastal California chaparral.
Grasslands are at great risk of invasion by woody species — both native and introduced — that can irretrievably alter these systems and affect the birds that rely on them. Although some grassland species, such as Loggerhead Shrike and Northern Bobwhite, are tolerant of some degree of woody plant cover, many other species of grassland birds, such as Chestnut-collared Longspur, will disappear with even a slight increase in woody shrubs. Other grasslands species particularly vulnerable to climate change include resident birds such as the Sharp-tailed Grouse and Greater and Lesser Prairie-Chicken and long distance migrants such as Wilson’s Phalarope, Dickcissel, and Bobolink.
Although birds of forests show relatively the least vulnerability to climate change of all habitats we analyzed, we nevertheless expect change to occur. Northward shifts in tree species’ ranges, increases in the frequency of insect outbreaks, longer and more severe fire seasons, and generally drier conditions will all result in changed bird species distributions.
Some of the most vulnerable forest species include those restricted to isolated, small habitat types in either the breeding or wintering season, such as Kirtland’s Warbler or Bicknell’s Thrush. Of most concern, however, are a group of species known as “aerial insectivores”, such as Black Swift, Whip-poor-will, and Chuck-will’s-widow, which, in addition to the factors listed above, are at risk from declines in their medium and large-bodied insect prey.
(Image: Bobolink, Chester County, Pennsylvania. Image credit: kellycolganazar/Flickr through a Creative Commons license.)
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