More than one-third of North America's 1,154 native bird species are at high risk of extinction due to climate change and other manmade factors, a new report found.
Thirty-seven percent of the continent's bird species across 10 different habitat types need "urgent conservation action," the North American Bird Conservation Initiative said in its annual "State of the Birds" report released Sunday. Forty-nine percent were identified as having moderate risk, while just 14 percent were marked as low risk.
Researchers categorized bird species based on their population size, population trends, population distribution and threats to both breeding and non-breeding members of the species.
The decline of bird species is most pronounced in ocean and tropical forest habitats, where more than half were identified as having a high risk of extinction and are on the organization's "Watch List."
"The outlook for oceanic birds — including seabirds and a group of landbirds found only on islands off the Mexican coast — is the bleakest of any North American bird group," with 57 percent of species in the "high risk" category, the report found. "Small and declining seabird populations are severely threatened by invasive predators on nesting islands and accidental bycatch by commercial fishing vessels, as well as overfishing of forage fish stocks, pollution, and climate change."
Some of the most threatened oceanic species include the Black-capped Petrel, the Fea's Petrel and the Bermuda Petrel.
J.D. Bergeron, the executive director of International Bird Rescue, said these findings were consistent with his organization's observations.
"We see rising numbers of seagoing and coastal birds struggling throughout the year, likely in response to poor food supply and changes to their traditional living environments," he said.
In tropical forest habitats, where 56 percent of species are in the high-risk category, deforestation and fragmentation -- a process of cutting down trees that leaves just small, isolated patches of forest behind -- have "reduced these continentally important habitats to precious small stands," the report says. The decline is most evident in Mexico's tropical forests, which have lost more than 70 percent of their bird habitats since the 1970s.
Coastal habitat populations, which rank as having the third most species at high risk of extinction, at 37 percent, are especially threatened by "sea-level rise, coastal development, disturbance from human recreational activities, and the threat of oil spills" all putting pressure on the mangroves, salt marshes and sandy beaches those birds rely on for breeding grounds.
John Marzluff, a professor of wildlife-habitat relationships and avian social ecology and demography at the University of Washington, said he wasn't surprised to see this report's findings and emphasized threats to bird species in grasslands, where 27 percent face a high chance of extinction, according to the report.
Those species "are especially threatened because of our past destruction of their habitats for agriculture," he wrote in an email to The Huffington Post. "These typically dry, 2-dimensional habitats are likely to be further degraded with climate change that may dry them further or favor tree growth as some of these areas receive greater rainfall in the future. Either is bad for species adapted to grasses and shrubs."
He hopes the next farm bill will ensure more protection for bird species in those habitats.
"Currently subsidies often promote ecologically damaging actions (increased area in monocultures of corn, for example)," Marzluff wrote. "By reducing the area planted, interspersing planted areas with grass or shrub leave areas, and setting aside conservation reserve lands planted with native grasses or shrubs, we could do a lot to further many vulnerable species."