Study indicates big loss of North American birds

A report issued by the Partners in Flight organization carries a sledgehammer of a delivery with its claim that the North American continent has lost 1.5 billion birds since the 1970s. That staggering figure is arrived at after the review of population surveys and studies conducted by a multitude of environmental agencies, government entities, and university programs.

“That number — 1.5 billion — is a very shocking number, and it is making people sit up and take notice, but we’ve known for a very long time that there is a serious problem with birds,” said Andrew Couturier, a senior analyst with Bird Studies Canada and one of the report’s co-authors. “It is very disheartening to see that, but maybe not surprising for those of us that work on these issues. A number of reports in both the U.S. and Canada indicate there has been a problem for some time, and that this is a major issue in our environment.”

The report cites many of what could be called the “usual suspects” as the likely causes of the population drops in certain more vulnerable species — development, pollution, habitat fragmentation, degradation and loss, the use of pesticides, collisions with wind turbines and buildings in the air column, and climate change.

“We believe there is a mixed bag of things interacting to cause this, with the background of land clearing. There just isn’t the available habitat that there used to be,” Couturier said last week from his office in Port Rowan, Ontario.

The report contends that the North American population of evening grosbeaks has fallen 92 percent since 1970, while the snowy owl has seen its numbers drop by 64 percent in the same time period. There are 86 species in an especially precarious position because of decreased populations, the report says, and nearly two dozen of those species have had their populations cut in half over the last four decades.

“The situation certainly seems to be grim for many of these species,” Couturier said, adding that the study projects that some of the more endangered bird species could experience another 50 percent drop in their populations over the next 40 years.

Couturier said the impact of these population losses can be seen in the Midwest in the declining numbers of chimney swifts, nighthawks, and other aerial insectivores.

“These have been some very iconic and familiar species in Ohio, but they are disappearing in a hurry,” he said. “The chimney swift has lost about 65 percent of its population since 1970. We would have seen the common nighthawk very frequently 40 years ago, but it has declined quickly. It is pretty much the same story with this whole group — some normally very abundant species are going downhill quite rapidly.”

The report reflects an ambitious effort to characterize bird populations across the breadth of the continent, and assess them over a nearly a half century period. It’s most basic conclusion is that many of our bird species are in dire straits, and the 1.5 billion figure illustrates a scientific best guess at what we have lost.

“The information on urgency is quite alarming,” Judith Kennedy of Environment Canada told the Canadian Press. She was another co-author of the Partners In Flight report. “We’re really getting down to the dregs of some of these populations.”

The report also cites a serious threat to many grassland birds, and species that rely on sagebrush or desert environments. The Gunnison sage grouse, ivory-billed woodpecker, and the long-troubled California condor also fall into the report’s list of species that are most vulnerable to extinction.

Earlier this year, biologists from Audubon published a study that concluded one-third of the birds that winter in North America have experienced population decreases over the last 50 years. The North American Bird Conservation Initiative went so far as to say that a third of our North American bird species risk extinction unless major conservation measures are enacted.

Mark Shieldcastle, the research director with the Black Swamp Bird Observatory based at Magee Marsh, said the recent report issued by the Partners in Flight organization leaves him with mixed feelings.

“In a sense the report and that 1.5 billion figure is shocking, but in another sense, the basic conclusion is not,” he said. “We are on a downhill slide with a lot of our species, but I have some questions about where they got their baseline data for this study. I’m not sure of the numbers that are involved since there were no population surveys on many of these species back in the 1970s, so I don’t have that much confidence in it without a lot more study.”

Couturier said the conclusions were reached after “all kinds of complicated and sophisticated” number crunching and reviews of previous population surveys.

“We figured the population trends and estimated the number of birds that would have existed in 1970, and then calculated the loss and also projected into the future,” he said. “We looked at information that we can gather from U.S. and Canada-wide surveys.”

Shieldcastle, who had a long and distinguished career as an avian biologist with the Ohio Department of Natural Resources, said he does not question the downward trend with many species, while also citing that other birds have had their numbers grow stronger in recent decades.

“The trajectory, the direction we are going with birds in general, is realistic, but are some of these species going down as much as this report says — I just don’t know,” he said. “There is a lot of conjecture and opinion going into those numbers.”

Shieldcastle said biologists are much better equipped today to collect data on the trends in bird populations, but not with all species, especially the long-distance migrants and the species that use the northern boreal forests for seasonal nesting.

“Overall, we are much better at this, but with some birds we are still in the dark ages,” he said.

Shieldcastle expects to see a significant improvement in the collection of data on bird species over the next decade with the use of tiny data loggers and satellite transmitters that will allow biologists to get a more complete picture of the species that migrate long distances.

“We’re right on the edge with a lot of this, so the report comes at a good time,” he said. “These birds have evolved and adjusted to changes over long periods of time, but there’s no question they face a lot of threats right now, so there is reason to have real concern.”

Couturier said international cooperation on bird studies is the best it has ever been, and an essential element in reversing the decline of many species.

“There is certainly plenty to be concerned about, but there is also reason to be hopeful, if we put our minds to it,” he said.