More Than Half of U.S. Bird Populations Are Shrinking | Science

golden-winged warbler

A golden-winged warbler perches on a branch in Minnesota. The bird’s declining population worries ornithologists.
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Interest in birds and birdwatching surged during the Covid-19 pandemic, with legions of birders, new and old, recording the details of their feathered sightings with apps such as eBird. In the process, these citizen scientists delivered a glut of high-resolution data that has been a boon to American ornithologists looking to better understand bird populations.

Combined with decades of traditional biological surveys, this trove of data tells a story, and not a happy one. A new report out today from more than 30 science and conservation groups finds the populations of more than half of a selection of 259 bird species from across the United States are declining.

The publication, called the 2022 U.S. State of the Birds Report, also identifies 70 birds perched on a precipice. These “tipping point” species—including the rufous hummingbird, golden-winged warbler and black-footed albatross—aren’t yet in sufficiently dire straits to be listed as federally endangered, but their populations exhibit such worrying trends that this next step is all but assured if nothing changes. In calling out these specific species, the report suggests prioritizing them for conservation before the last-ditch effort of an Endangered Species Act (ESA) listing becomes necessary.

The grim findings echo those of a headline-making 2019 paper published in the journal Science that estimated North America had lost three billion individual birds since 1970.

“Bird populations provide important information about the state of the environment—environments that we as humans also depend upon,” says Amanda Rodewald, an ornithologist at Cornell University and the co-chair of the science committee behind the report. “When we look at groups of birds seeing steep declines that’s a warning for us as well.”

The causes of this now firmly established decline can be complex for some individual species, but the biggest single threat is habitat loss, says Rodewald.

Peter Marra, an avian ecologist at Georgetown University and a contributing researcher on State of the Birds, thinks about habitat loss anytime he’s in an airplane flying over the U.S.

“If you look out the window you can’t help but see how much we’ve manipulated the landscape,” says Marra, who formerly directed the Smithsonian Migratory Bird Center. “At least a third of the landscape has been converted or transformed—of course we’ve lost so many birds.”

To assess population trends of North American birds from a variety of habitats and evolutionary groups, the report combined data from five multi-decade surveys, including those performed by citizen scientists, and subjected those data to statistical analysis. This allowed the massive team of researchers to break down population health by habitat type, region and species going back to 1970.

The report cites a broad trend of declines caused by some combination of habitat loss, climate change, predation by domestic cats, invasive species and other threats, with one notable exception. The populations of waterfowl—such as ducks, geese and swans that inhabit inland lakes, ponds and wetlands—are increasing. Ruth Bennett, an ecologist at the Smithsonian Conservation Biology Institute’s Migratory Bird Center and co-producer of the report, points to the positive actions taken by hunters and fishers who collectively prioritized preserving these species’ habitats so hunting could continue as the biggest reasons for this bright spot.

“Without the hunting and fishing community these birds would have had the same trajectory as all these other species,” says Bennett. “Hunting groups and federal agencies recognized that these birds were declining and took action. It’s really a conservation success story and it goes to show what’s possible when there is enough money and political will to protect birds.”

Ring-necked ducks

Ring-necked ducks swim on a pond in Washington state. The new report finds waterfowl are increasing in the U.S.

Wolfgang Kaehler / LightRocket via Getty Images

Meanwhile, the fastest declining groups are grassland birds, such as the mountain plover, and shorebirds, such as the lesser yellowleg, which have each lost roughly a third of their numbers since 1970.

In the Great Plains, humans have converted grasslands to increasingly intensive forms of agriculture that have dramatically reduced native prairielands. For shorebirds, the primary threat is the allure of coastal real estate and the associated destruction of key bird habitats to accomdate this demand.

The 70 newly identified tipping point species have each lost half or more of their populations over the last half-century and are on track to be slashed in half yet again in the next 50 years if nothing changes. “The hope is that by identifying these species we can motivate action proactively to avoid an ESA listing,” says Rodewald. “Knowledge is power. We can see this train coming at us and we have the ability to avoid it.”

The report’s authors say the sooner action comes, the more likely the species’ declines can be stopped and the less costly and less disruptive interventions would be for nearby human communities. Many of the 70 species on the list already have dedicated groups working toward developing or executing conservation plans, but for those that don’t or that require an extra push to get over the hump in terms of organizing, the hope is that the list provides something to rally around, says Bennett.

Apart from its empirical findings, the report also aims to show how bird conservation can benefit human communities. At the local level, protecting and restoring wetlands favored by birds can provide nearby towns with flood mitigation as well as improved water quality and quantity. In urban areas, green space provides neighborhoods relief from extreme heat while also creating refuge for birds. At the national level, boosting bird habitat can help fight climate change by removing carbon dioxide from the atmosphere and storing it in living plant tissues and soils. The report estimates that the added carbon storage from implementing major bird conservation ventures in the Appalachian Mountains, the Lower Mississippi Valley, the Prairie Pothole region and California’s Central Valley would be roughly equivalent to removing the emissions from more than two million vehicles per year over the next two decades.

Including local communities in conservation plans and touting the potential human benefits of protecting ecosystems reflects a somewhat recent change in conservationists’ tune, says Scott Edwards, an ornithologist at Harvard University who wasn’t involved in the report. “Conservation has evolved from buying up land and keeping people out to a place where it deals with and works with the fact that humans live everywhere,” says Edwards. “Humans are part of the global ecosystem so we can’t leave humans out of the equation.”

To that end, the report outlines a step-by-step approach to conserving birds that begins with identifying the causes of decline but also includes co-creating solutions to address those causes with local communities to ensure conservation helps them too.

For example, in the Southwest, around the Rio Grande, Indigenous communities such as the Pueblos of Santa Ana, Isleta, Sandia and Ohkay Owingeh have been working to restore the river’s backwaters and oxbows, which have all but disappeared following decades of channelization. These ephemeral meadows, floodplains and wetlands lay at the center of cultural practices such as the collection of medicinal plants and are also key habitats for endangered birds including the Southwestern willow flycatcher and Western yellow-billed cuckoo. By working together with bird conservation groups and government agencies, these Indigenous communities are finding ways to preserve their heritage and endangered wildlife.

Restoring bird habitat can also take the form of forest management. In the Pacific Northwest, climate change and decades of fire suppression have created dense overgrown forests that threaten Oregon towns such as Ashland and Medford with extreme wildfires. These forests used to burn much more frequently but at much lower intensity, creating a mosaic of different habitat types for birds that have since become threatened. Management practices including forest thinning, fuel removal and the use of prescribed fire could bring back habitats that reverse the declines of species such as the olive-sided flycatcher and rufous hummingbird while protecting the Oregon communities.

Marra says he hopes the report ends up in the hands of decision-makers and that it can sound the alarm on the severity of the problems facing birds in the U.S. while also showing that, with sufficient funding and political will, we know how to solve them.

“Reports like this put such a useful and informative lens on our ecosystem health,” says Edwards. “But they’re not just for coffee table reading, now we have to take action.”

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