Large decline in bird numbers causes concern for ecosystem health

Apr. 24—CHEYENNE — Picture a lemon-breasted western meadowlark perched atop a fence post. He's singing that crystalline meadowlark song, the one that flows like water into your ears across a still, greening prairie. Or maybe a red-breast robin bob-bob-bobbing for worms in the green grass of your backyard.

Pretty spring pictures, aren't they?

But the thing you might not see — or at least take notice of — is how there has been a massive decline in bird numbers across the North American continent during the last half century, a decline that includes both of these birds.

The research

According to an October 2019 research article in the journal Science, 11 biologists from big-time bird research centers like Cornell University's Ornithology Lab, the American Bird Conservancy, the Patuxent Wildlife Research Center, the U.S. Geological Survey and the Smithsonian's Conservation Biology Institute say there has been a significant decline in bird populations across North America.

How much? The article "Decline of the North American avifauna" says the net loss approaches 3 billion — with a B — birds. This represents a loss of 29%, nearly a third, of the bird life tallied in 1970.

Their research also indicated that there has been a "steep decline" in biomass (the number of birds) observed during fall and spring migrations during a recent 10-year period.

The biologists looked at population changes among 529 bird species — 76% of all breeding birds — in the continental U.S. and Canada across almost 50 years of population data. They also used a network of 143 NEXRAD weather radar systems across the U.S. to estimate how many birds migrated at night from 2007 to 2017.

The results show a net loss of somewhere between 2.7 million and 3.1 billion birds since 1970. And the radar counts showed a reduction of about 14% of total biomass (night-migrating bird life) across that 10-year span. Most of that biomass reduction took place in the eastern U.S., where night-time migrations are dominated by "temperate and boreal-breeding songbirds." The Pacific and Central flyways, which includes Wyoming, showed no consistent trends.

Some 57% of the 529 bird species considered in the study showed 50-year declines. Grassland birds had the biggest drop, 53% among 31 species, representing more than 700 million birds. The report says 74% of grassland bird species are declining.

Forest birds were also down by 1 billion birds since 1970.

More than 90% of the total losses fell in a dozen bird families including sparrows, warblers and blackbirds and finches. Also, 19 widespread and abundant land-based birds saw population declines of 50 million. This included two introduced, non-native species of Old World sparrows.

A total of 419 native migratory birds — finches, swallows, flycatchers, thrushes, sparrows, warblers and blackbirds — showed a net loss of 2.5 billion individuals. Those that wintered in temperate areas, such as the U.S. South, lost 1.4 billion of their kind, particularly in coastal areas. Those who trekked to the Southwest's arid lands dropped 42%, South American winterers lost 40%.

"This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function and services," their research notes.

Local bird losses

What about Wyoming — specifically Cheyenne?

Well-known local birdwatcher and Cheyenne-High Plains Audubon Society member Barb Gorges says it is kind of hard to acknowledge the local losses of birds the study points out without hard data to back it up.

However, she points to CHPAS's Big Day spring bird counts. These are timed to take place during the height of spring migration, when bird numbers are up. Each Big Day count participant or group of people try to tally as many species of birds as they can find. Gorges said Big Day counts started in the 1950s — she and husband Mark got involved during the 1990s.

Back then, she said, she recalled people tallying 140 to 150 unique species. Recent counts struggle to hit 100 species.

"I'm not sure what causes the difference," Gorges said. "Is it the number of people involved? (Fewer now.) So you're not comparing apples and apples, but apples and oranges."

Anna Chalfoun can provide some Wyoming numbers.

Chalfoun is assistant unit leader at the U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, and an associate professor within the Department of Zoology and Physiology at the University of Wyoming.

"Unfortunately," Chalfoun says, "similar to the range-wide trends, we have a lot of declining bird populations here in Wyoming."

"One of the highest-profile species, of course, is the greater sage-grouse, which has been petitioned for endangered species status multiple times. Wyoming also is home to the three migratory songbirds considered sagebrush obligates (dependent upon sage-steppe environments), and all three species also are in decline in Wyoming as per the USGS Breeding Bird Survey: Brewer's sparrow (-1.5% in Wyoming, -0.9% range-wide); sage thrasher (-0.5% in WY, -0.4% range-wide); sagebrush sparrow (-1.2% range-wide, but stable in WY)."

"Our grassland songbirds also are not faring well," Chalfoun continued. "For example, the McCown's longspur, which inhabits our shortgrass and mixed-grass prairies, is declining at a rate of -2.13% per year since 1966. Even some of our more common grassland birds that are the harbingers of spring, such as the western meadowlark, are declining (almost 1% per year, range-wide).

"My colleague, Don Delong of the U.S. Forest Service, also recently brought to my attention some very concerning trends in our forest songbirds. The stunning evening grosbeak, for example, has declined by almost 5% per year in Wyoming since 1966 (-2.5% range-wide).

"Finally, another group of concern is our alpine species. The black rosy-finch, for example, breeds at some of the highest elevations of any North American bird, and is therefore one of the least-studied species. Alpine wildlife are some of those at most risk from a changing climate. Hence, similar to the sage-grouse, rosy-finches are a watch list species for the group Partners in Flight."

Why are grassland birds in the highest decline?

"Most evidence points to the drastic loss and alteration of North America's grassland habitats," Chalfoun said. "The most extreme example is that we have only a tiny fraction of our original tallgrass prairie habitats remaining in the Midwest."

"However, for the non-game birds — songbirds — we know very little about potential limiting factors outside of the nesting period (post-fledging, migration, over-wintering)," Chalfoun continued. "This is, in part, because of funding and historic technological limitations. Transmitters small enough to put on tiny birds are not available."

"My lab is beginning work on sagebrush songbirds," she said. "However, that will focus on the full annual cycle — nesting, post-fledging, migratory routes, over-wintering locations. We will be putting light-level geolocator tags on birds to determine where they migrate and over-winter, and solar-powered tags with which we can assess movements, return rates and annual survival."

The research study specifically pointed to habitat loss; toxic pesticide use in breeding and wintering areas; agricultural intensification; urbanization; and declines in insect numbers and diversity as source for bird population declines.

Fewer birds — so what?

Why is this decline in bird numbers important?

From an environmental standpoint, birds literally are the "canary in the coal mine." They can indicate if something is wrong with the ecosystem, and the unstated, yet fairly obvious conclusion of the study is that there is something wrong.

The biologists' report says, "The long developing, but overlooked biodiversity crisis in North America is not restricted to rare and threatened species, but includes many widespread and common species that may be disproportionately influential components of food webs and ecosystem function."

"Declines in abundance can degrade ecosystem integrity, reducing vital ecological, evolutionary, economic and social services," the report continues. "Birds may also foreshadow a much larger problem indicating similar or greater losses in other taxonomic groups."

Birds function as important pollinators, seed dispersers and pest controllers in crops, and represent an important part of the economy. Some 47 million people spend $9.3 billion annually via bird-related activities in the U.S. alone.

"Our migratory songbirds primarily consume arthropods (insects and spiders) during the breeding season," Chalfoun pointed out. "So think about how many insect pests that are likely to be consumed when you multiply thousands of birds that are constantly foraging! Many birds are also involved in pollination. And our songbirds are beautiful, as are their songs. The birding industry is a huge market in the U.S."

What can be done to stem the tide of the decline?

"The answer to this is likely context- and species-specific," said Chalfoun. "For some species, the prioritization of remaining high-quality nesting habitat may be sufficient. For some, we may also need to think about conditions along migratory stopover sites and/or over-wintering grounds in Mexico, the Caribbean, and Central and South America. So the problems become international."

"Slowing the rate of climatic change will be really important," she said, "as changing temperatures are causing mismatches in the migratory and nesting timing of birds and their main food sources, and more frequent and intense storms are causing some mass mortalities. For some species, specific management intervention may be necessary."

According to the biologists' report, the decline in bird numbers is likely to continue without "... targeted conservation action, triggering additional endangered species listings at tremendous financial and social cost."

Good news on the bird front?

While the research report had a lot of bad news, it wasn't all bad.

Chalfoun pointed to species that have been the focus of a lot of conservation work — raptors (hawks, owls, eagles) and waterfowl — and noted how these species have rebounded in numbers.

The report shows that while 3 billion songbirds have been lost in the last 50 years, 250 million other birds have increased. This includes turkeys and grouse, raptors, gnatcatchers, waterfowl (ducks and geese), vireos and 21 other families of birds.

"Many species of waterfowl and waterbirds have benefitted from widespread wetlands restoration and mitigation efforts," Chalfoun noted. "And the banning of DDT helped stop the widespread nesting failures of many raptors. (DDT led to eggshell thinning.) These are hopeful stories that demonstrate that we can reverse declines and bring endangered birds back from the brink."

"The extent of the challenge can be overwhelming, especially for those of us that think about wildlife conservation every day. But I think the examples above provide hope," she said.

Many people are working on finding ways to restore populations of declining birds, she continued.

"Unfortunately, it takes time to conduct the rigorous studies and generate the information on which to base sound management and mitigation practices," she said. "As the co-chair of the Conservation Committee of the American Ornithological Society, we are working on ways to provide some funding to folks conducting work on birds in Latin America, to facilitate more full-annual cycle understanding for more species of concern."

John D. Taylor is the Wyoming Tribune Eagle's assistant managing editor. Email: jtaylor@wyomingnews.com.