Study says bird populations declined nearly 30% in 50 years
Here is some very sobering news provided by both the American Bird Conservancy and the Cornell Laboratory of Ornithology.
It comes from an article published Sept. 19 in “Science” magazine, which says North America’s bird populations have declined by 29 percent since 1970.
Take note, too, that good news comes about for waterfowl. Credit on that score is being given by Cornell to the nation’s hunters for their contribution to waterfowl conservation through the license fees and “duck-hunting” stamps required to be purchased. These monies have gone toward wetlands preservation, protection and acquisition, Cornell says.
Here, then is Cornell’s statement:
A study published today in the journal Science reveals that since 1970, bird populations in the United States and Canada have declined by 29 percent, or almost three billion birds, signaling a widespread ecological crisis.
The results show tremendous losses across diverse groups of birds and habitats—from iconic songsters such as meadowlarks to long-distance migrants such as swallows and backyard birds including sparrows.
“Multiple, independent lines of evidence show a massive reduction in the abundance of birds,” said Ken Rosenberg, the study’s lead author and a senior scientist at the Cornell Lab of Ornithology and American Bird Conservancy.
“We expected to see continuing declines of threatened species. But for the first time, the results also showed pervasive losses among common birds across all habitats, including backyard birds.”
The study notes that birds are indicators of environmental health, signaling that natural systems across the U.S. and Canada are now being so severely impacted by human activities that they no longer support the same robust wildlife populations.
The findings show that of nearly three billion birds lost, 90 percent belong to 12 bird families, including sparrows, warblers, finches, and swallows—common, widespread species that play influential roles in food webs and ecosystem functioning, from seed dispersal to pest control.
Among the steep declines noted:
Grassland birds are especially hard hit, with a 53-percent reduction in population—more than 720 million birds—since 1970.
Shorebirds, most of which frequent sensitive coastal habitats, were already at dangerously low numbers and have lost more than one-third of their population.
The volume of spring migration, measured by radar in the night skies, has dropped by 14 percent in just the past decade.
“These data are consistent with what we’re seeing elsewhere with other taxa showing massive declines, including insects and amphibians,” said coauthor Peter Marra, senior scientist emeritus and former head of the Smithsonian Migratory Bird Center and now director of the Georgetown Environment Initiative at Georgetown University.
“It’s imperative to address immediate and ongoing threats, both because the domino effects can lead to the decay of ecosystems that humans depend on for our own health and livelihoods—and because people all over the world cherish birds in their own right. Can you imagine a world without birdsong?”
Evidence for the declines emerged from detection of migratory birds in the air from 143 NEXRAD weather radar stations across the continent in a period spanning over 10 years, as well as from nearly 50 years of data collected through multiple monitoring efforts on the ground.
“Citizen-science participants contributed critical scientific data to show the international scale of losses of birds,” said coauthor John Sauer of the U.S. Geological Survey (USGS). “Our results also provide insights into actions we can take to reverse the declines.”
The analysis included citizen-science data from the North American Breeding Bird Survey coordinated by the USGS and the Canadian Wildlife Service—the main sources of long-term, large-scale population data for North American birds—the Audubon Christmas Bird Count, and Manomet’s International Shorebird Survey.
Although the study did not analyze the causes of declines, it noted that the steep drop in North American birds parallels the losses of birds elsewhere in the world, suggesting multiple interacting causes that reduce breeding success and increase mortality.
It noted that the largest factor driving these declines is likely the widespread loss and degradation of habitat, especially due to agricultural intensification and urbanization.
Other studies have documented mortality from predation by free-roaming domestic cats; collisions with glass, buildings, and other structures; and pervasive use of pesticides associated with widespread declines in insects, an essential food source for birds.