Birds in every habitat will be affected by climate change.

In this report, we address climate change--focusing attention on what may be in store for our nation’s birdlife, and the stories the birds themselves are telling us about the changes that are happening even now.

Pelican Island courtesy USFWS

Birds in every terrestrial and aquatic habitat will be affected by climate change, although individual species in each habitat are likely to respond differently. We assessed the relative vulnerability of each United States bird species, based on five biological aspects of sensitivity to climate change, as well as the exposure of each species' habitat to climate change in the near future. We then categorized species as showing High Vulnerability (a vulnerability score of four or more), Medium Vulnerability (a vulnerability score of two or three), or Low Vulnerability (a vulnerability score of zero or one). (See Methods)

The results indicate that a majority of birds dependent on oceans, and birds on Hawaiian Islands, are highly vulnerable to climate change. Birds in coastal, arctic/alpine, and grassland habitats, as well as those on Caribbean and other Pacific islands show intermediate levels of vulnerability. Most birds in aridlands, wetlands, and forests show lower overall vulnerability (see bar graph).

Across all habitats, species of conservation concern showed higher levels of vulnerability to climate change than species not threatened by other factors. Vulnerability to climate change may hasten declines or prevent recovery. At the same time, increased conservation concern may be warranted for groups of birds, such as waterfowl and aerial insect-eating birds that are abundant now but that will be increasingly stressed as climate change impacts intensify.

Big Changes are in Store for Oceanic Birds

All 67 oceanic bird species, including albatrosses, petrels, tropical terns, tropicbirds, frigatebirds, and puffins are vulnerable because of their low reproductive potential, use of islands for nesting, and reliance on rapidly changing marine ecosystems. Seabirds such as Laysan Albatross and Bonin Petrel that are restricted to nesting on low-lying islands are in danger of losing their breeding habitat as sea levels rise. To provide oceanic bird populations with the best chances of adapting to climate change, we must reduce existing threats from overfishing, fisheries bycatch, and pollution. We must also take proactive measures such as removing invasive species and protecting existing or potential breeding colonies on high islands.

Sea Level Rise and Increased Storm Activity Threaten Coastal Birds

Rising sea levels are expected to inundate or fragment low-lying habitats such as salt marshes, sandy beaches, barrier islands, and mudflats. Increasing frequency and severity of storms and changes in water temperatures will impact quality and quantity of coastal habitats and alter marine food webs. Beach-nesting terns, highly specialized Saltmarsh Sparrows, and birds dependent on marine waters are among the most vulnerable species. Migratory species such as shorebirds are also vulnerable to changes in stopover and wintering habitats. Conserving coastal habitats will require planning and management to facilitate birds’ movement and resilience. 

Accelerated Changes in Arctic/Alpine Regions

Increased temperatures will drastically alter surface water and vegetation in the arctic, resulting in major changes in bird abundance and distribution. White-tailed Ptarmigan and rosy-finches may disappear from mountaintops as alpine tundra diminishes. Species that depend on grass-sedge tundra for breeding, such as the Black Turnstone, could lose their tundra breeding habitat. Minimizing human-caused disturbance to low-lying tundra and high-elevation alpine habitats may help the most vulnerable species adapt to changes.

Laysan Finch by James H. Breeden, USGS

Birds of Hawai'i and other Pacific islands already face multiple threats and are increasingly challenged by mosquito-borne diseases and invasive species as climate change alters their native habitats. Protection and restoration of natural systems is essential to endangered species such as Puaiohi and ’Akiapōlā’au in Hawai'i and the Puerto Rican Parrot. Decreased rainfall will reduce habitat for high-elevation forest birds and may result in breeding failures among resident birds and reduced overwinter survival of migrants in the Caribbean.

Changes in Rainfall and Temperature will Impact Wetland Birds

Predicted changes in temperature and rainfall will probably reduce vital habitats for waterfowl and other wetland birds. Additionally, these changes will reduce the ability of wetlands to provide functions such as flood control, sediment capture, and replenishing groundwater. Climate change could reverse the positive effects of conservation actions that have increased waterfowl populations. In the Prairie Pothole region alone, increased drought conditions and loss of wetlands could lead to significant reductions in breeding waterfowl. Conservation programs must be expanded to include climate change impacts in biological planning, conservation design, and habitat protection initiatives.

Sonoran Desert courtesy USFWS

Aridlands and grasslands are predicted to become warmer and drier. Many aridland birds are at increased risk because of drought and the potential for summertime temperatures greater than they can tolerate. Important wintering areas for many grassland birds may become unsuitable due to increased drought, invasive species, and invasion by woody shrubs. Prairie grouse and sage-grouse are vulnerable because of high site fidelity and their lack of tolerance for intensifying agricultural and energy development. Habitat corridors will be vital to allow birds to move to more suitable areas. Habitat conservation and the protection of core areas in cooperation with farmers and ranchers will be required for grassland and aridland birds.

Subtle Changes for Forest Birds

Forests will gradually change as precipitation changes, and as fire, insect pests, and diseases alter forest communities. Forest types in eastern states are predicted to shift northward, whereas western forest types will shift to higher elevations. These changes will alter bird communities, although most forest birds will probably be resilient because of their large distributions and high reproductive rate. However, long-distance migrants, especially aerial insect-eaters such as swifts and nightjars, may face multiple challenges such as the timing of food resource availability throughout their migratory range. Long-term management solutions should include protecting large forest blocks with the highest carbon stores and connecting landscapes by creating corridors.

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