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Biodiversity: One in four U.S. birds imperiled

2011 State of the Birds report highlight public lands, climate-change threats

Oceanic birds and birds that rely on coastal habitat face challenges related to climate change, according to the 2011 State of the Birds report. PHOTO BY BOB BERWYN.

SUMMIT COUNTY — A quarter of all bird species living in the United State are imperiled or in decline, according to the 2011 State of the Birds report from the U.S. Department of Interior.

This year’s report focuses on public lands, pointing that, of the more than 1,000 bird species living in the country, 251 are federally listed as threatened, endangered or as species of conservation concern.

“The State of the Birds report is a measurable indicator of how well we are fulfilling our shared role as stewards of our nation’s public lands and waters,” Interior Secretary Ken Salazar said in a release. “Although we have made enormous progress in conserving habitat on public lands, we clearly have much more work to do. The good news is that because birds so extensively use public lands and waters as habitat, effective management and conservation efforts can make a significant difference in whether these species recover or slide towards extinction.”

Publicly owned lands support at least half of the entire U.S. distributions of more than 300 bird species. The findings indicate tremendous potential for bird conservation, as well as some challenges, including rampant energy development across crucial sagebrush habitat in the West and threats to habitat from declining forests and climate change.

The report assessed the distribution of birds on nearly 850 million acres of public land and 3.5 million square miles of ocean. It relied on high-performance computing techniques to generate detailed bird distribution maps based on citizen-science data reported to eBird and information from the U.S. Geological Survey’s Protected Areas Database of the United States.

Coastal and ocean bird habitat is under severe stress, with at least 39 percent of bird species in those ecosystems declining, and almost half listed as species of conservation concern, the report concludes.
The situation is even more critical in the West, where 75 percent of bird species that rely on arid -land habitat are declining, and 39 percent are listed as species of conservation concern.

Hawaii is also a hotspot of concern, with more birds are in danger of extinction than anywhere else in the U.S. Public lands in Hawaii support 73 percent of the distribution of declining forest birds. Among declining Hawaiian forest birds on Kauai, about 78 percent rely on state land. Four endangered species in the Northwest Hawaiian Islands are entirely dependent on federal lands.

Grassland birds are among the nation’s fastest declining species, yet only a small amount — 13 percent — of grassland is publicly owned and managed primarily for conservation. Forty-eight percent of grassland-breeding bird species are of conservation concern, including four with
endangered populations.

Wetlands may be a bright spot in the bird conservation picture, as nearly 30 million acres of wetlands have been acquired and managed to help restore bird populations. Populations of some game species have increased by more than 100 percent during that span.

Climate change

Last year’s report included an extensive section on climate change, explaining that all 67 U.S. species of oceanic birds are very vulnerable to climate change impacts because of their low reproductive rates, use of islands for nesting and their reliance on rapidly changing marine ecosystems.

“Seabirds such as the Laysan albatross and Bonin petrel are in danger of losing their breeding habitat as sea levels rise. To provoke oceanic bird populations with the best chance of adapting to climate change, we must reduce existing threats from over-fishing, fisheries by-catch, and pollution. We must also take proactive measures such as removing invasive species and protecting existing or potential breeding colonies on high islands,” according to the report.

Ocean birds are also slower to recover from adverse conditions because of lower breeding rates and high mortality rates among young birds. Sea birds forage over vast areas and are very sensitive to the availability of marine food. The report explains that reproductive failure of seabirds has already been documented as a consequence of existing natural cycles — for example when seabird chicks starve during El Niño years.

If those cycles are amplified by climate change, and if extreme weather events become more common as predicted by most climate change models, population recovery is less likely. Warmer waters have already decreased the abundance of food for fish in Prince William Sound, the Gulf of Alaska and the California Current region, likely resulting in fewer fish-eating birds in those areas.

Birds that rely on temperatures cues to breed may fail to raise any young if their chicks hatch at the wrong time and miss the window when food is abundant. Climate change could also cause changes in the distribution of prey species, leading to declines in birds of they are unable to respond to those changes. Receding sea ice could make it impossible for arctic-breeding seabirds to reach foraging areas and return to their nests in time to feed chicks.

Oceanic birds are the most susceptible to climate change impacts, but birds relying on coastal, arctic/alpine and grassland habitats could also be hit hard by global warming. Most birds in arid lands, wetlands and forests show a lower overall vulnerability to climate change, the report concludes.

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