At the beginning of this month when about 5,000 red-winged blackbirds fell from the sky in one night in Arkansas, biologists were called on to put a damper on public speculation about pesticides and secret military tests by reminding everyone how many birds there are and how many die. They often do so as a result of human activity, but in far more mundane and dispiriting ways than conspiracy buffs might imagine.
“Five billion birds die in the U.S. every year,” said Melanie Driscoll, a biologist and director of bird conservation for the Gulf of Mexico and Mississippi Flyway for the National Audubon Society.
That’s from “Conspiracies Don’t Kill Birds. People, However, Do,” a NY Times story on the hot eco-topic du jour. The five billion number may seem high, but Birds Etcetera did a literature review in 20o2 that seems consistent with it. A 1997 Biodiversity and Conservation study, “How many birds are there?” found “different methods yield surprisingly consistent estimates of a global bird population of between 200 billion and 400 billion individuals.”
Here’s more of the NYT story:
That means that on average, 13.7 million birds die in this country every day. This number, while large, needs to be put into context. The federal Fish and Wildlife Service estimates that a minimum of 10 billion birds breed in the United States every year and that as many as 20 billion may be in the country during the fall migratory season.
Even without humans, tens of millions of birds would be lost each year to natural predators and natural accidents “” millions of fledglings die during their first attempts at flight. But according to the Fish and Wildlife Service, people have severely complicated the task of survival. Although mortality rates are difficult to calculate for certain, using modeling and other methods like extrapolation from local research findings, the government has come up with estimates of how many birds die from various causes in the United States.
Some of the biggest death traps are surprising. Almost everyone has an experience with a pet proudly bringing home a songbird in its jaws. Nationally, domestic and feral cats kill hundreds of millions of birds each year, according to the government. One study done in Wisconsin found that domestic rural cats alone (thus excluding a large number of suburban and urban cats) killed roughly 39 million birds a year.
Pesticides kill 72 million birds directly, but an unknown and probably larger number ingest the poisons and die later unseen. Orphaned chicks also go uncounted.
And then there is flying into objects, which is most likely what killed the birds in Arkansas. The government estimates that strikes against building windows alone account for anywhere from 97 million to nearly 976 million bird deaths a year. Cars kill another 60 million or so. High-tension transmission and power distribution lines are also deadly obstacles. Extrapolating from European studies, the Fish and Wildlife Service estimates 174 million birds die each year by flying into these wires. None of these numbers take into account the largest killer of birds in America: loss of habitat to development.
All of this explains why about a quarter of the 836 species of birds protected under the Migratory Bird Treaty Act are in serious decline. For a third of the other birds there is not enough information to be sure about the health of their populations.
Of course, poisons and electric wires are not as exciting to think about as secret government plots, but Ms. Driscoll says it is time we pay attention to them anyway.
“It is the story that the press and the public have largely missed, and it is important, and timely, given the current concern,” she said. “And it is what gets those of us who work in bird conservation motivated every day to try to deal with human-induced changes to our habitats, our landscape and our very climate.”
Treehugger has some good commentary on the I story:
Ultimately, the public’s fascination with the die-offs is rooted in the concern that all may not be right between man and nature — and that perhaps finally the scales have been tipped irrevocably, meaning we may be next. But as the stories fade from the headlines, perhaps we’ll be too enraptured in the next news cycle to even breathe a sigh of relief that the problem has ‘passed’, so we’ll carry on.
There is indeed something troubling about those mass deaths, but whether or not human activities are responsible for a few thousand bird corpses here and there isn’t really the point. 13.7 million wild birds died today in the United States and it’s unmentioned because there’s little doubt that we have something to do with most them.
Whatever the cause of the individual die offs, we ain’t seen nothing yet. Humans are in the process of making the planet very inhospitable to most species and the entire food chain:
- Royal Society: “There are very strong indications that the current rate of species extinctions far exceeds anything in the fossil record.”
- Veron: The end is in sight for the world’s coral reefs
- Nature: “Global warming blamed for 40% decline in the ocean’s phytoplankton”: “Microscopic life crucial to the marine food chain is dying out. The consequences could be catastrophic.”
- Must-read NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path.
- Geological Society: Acidifying oceans spell marine biological meltdown “by end of century”
- Science stunner: On our current emissions path, CO2 levels in 2100 will hit levels last seen when the Earth was 29°F (16°C) hotter