The decline of bird species throughout North America, experts say, is the proverbial canary in the coal mine.
A study led by the Cornell Laboratory of Ornithology — in collaboration with the U.S. Geological Survey and citizen groups — estimates that the continent has 3 billion fewer birds than it did 50 years ago. That represents 29 percent of North America’s bird population, with declines being seen across a wide range of species.
For the most part, this decline is steady and unrecognizable except to ardent bird watchers. But it reflects the continued degradation of ecosystems that adds up to a biodiversity crisis. A recent United Nations report, for example, warned that 1 million animal and plant species are at risk of extinction as humans invade natural habitats and the planet warms.
While the latest study focused on North American birds, the phenomenon is not unique to this part of the world. A 2014 study estimated that Europe had seen a decline of 421 million birds over 30 years; and a report this month from German scientists found that Lake Constance, at the border of Germany and Switzerland, has lost 25 percent of its birds in three decades.
Richard Gregory of University College London, told The Washington Post: “Studies like this do suggest the potential of a systems collapse. These birds are an indicator of ecosystem health. And that, ultimately, may be linked to the productivity and sustainability of agricultural systems.”
In North America, the decline is primarily among sparrows, warblers, blackbirds, larks, finches and other common birds. There is, however, some good news: An increase in waterfowl and raptors (such as eagles) has been quantified, likely a result conservation efforts and protective legislation.
Many of the disappearing species are insect-eaters, a fact that demonstrates the interconnectivity of nature. As Michael Parr of the American Bird Conservancy wrote for The Washington Post: “Birds are a part of the natural food chain, and this loss of birds represents a loss of ecological integrity that, along with climate change, suggests that nature as we know it is beginning to die.”
Birds eat insects, disperse seeds and serve as predators as well as prey. In one example of their benefits, their role in insect control is important for sustainable agriculture as birds reduce the need for chemical insecticides. And studies have shown that birds save conifer farmers in the Northwest hundreds of dollars per hectare by eating harmful insects.
The study does not specify the reasons for the decline, but ornithologists offer recommendations for how the average person can help protect bird populations. One is to keep house cats indoors; a study led by Oklahoma State University and the U.S. Fish and Wildlife Service estimates that cats kill 2.6 billion birds a year. Advocates also recommend increased regulation over the use of pesticides known as neonicotinoids, a reduction in littering and pollution (particularly plastics) and increased tree cover for nesting and protection.
Scientists note that the decline in North America’s bird population is not a call for drastic measures. But it is a call for recognition of a changing environment and for legislative and conservation efforts that better protect that environment.
As Parr, from the American Bird Conservancy, writes: “It is simply data that we can choose to act on — or not. It’s a bit like hearing you have elevated cholesterol: You can choose to ignore it, but if you do, worse consequences likely await.”
