Hundreds of Millions of Songbirds Are Disappearing
You might think that what happened to the passenger pigeon couldn’t happen today. We know better than to allow a species with a population in the billions to dwindle away to nothing over the course of a few decades, don’t we?
Sadly, no. In fact, it’s not just one species this time. It’s an entire world of migratory songbirds—turtledoves, skylarks, cerulean warblers, wood thrushes, yellow-breasted buntings, and many more—on flyways touching every continent.
The sort of industrial-scale hunting that wiped out the passenger pigeons a century ago is once again part of the story: For instance, a study early this year estimated that hunters and trappers, mostly in the eastern Mediterranean, are illegally taking 11 million to 36 million birds each year for food, the pet trade, and sport. Likewise, hunting of entire flocks in China has caused a 90 percent decline in populations of yellow-breasted buntings, once common across Eurasia but now more easily found on the dinner plates of the nouveaux riches.
But while the scale of this needless killing is shocking, the bigger problem for migratory birds, according to a new analysis published in the journal Science, is less sensational but even harder to address—“land-use changes and connected habitat degradation and loss.”
Franz Bairlein, director of the Institute of Avian Research in Wilhelmshaven, Germany, set out to write his analysis for Science, he said in an interview, when he realized that the headline-making study of killings did little to explain the steep migratory songbird declines in Western Europe. Those birds travel the western flyway back and forth to West Africa, largely bypassing the areas where the hunting of songbirds is a major problem. Yet when Europeans walk out the door these days, they hear or see an estimated 421 million fewer birds than in 1980.
That’s partly because the expansion and intensification of agriculture in Europe displaced natural habitat from the mid-20th century onward. That same trade-off is now also taking place, Bairlein said, at critical stopover points on the southern end of the flyway—particularly the Maghreb region (primarily Morocco and Algeria), to the north of the Sahara, and again in the Sahel (Burkina Faso, southern Mali, Ivory Coast, Ghana, and others), just south of the Sahara.
“Crossing ecological obstacles like oceans or deserts, these birds have to prepare by tremendous fattening as fuel for their flights,” said Bairlein. Natural habitat on either side of the long flight across the desert functions for birds “like our gas stations, where they have to fill up prior to and after the desert.” But both regions are “currently suffering population growth, overgrazing,” and the rapid loss of natural habitat to make room for increasingly intensive agriculture. As a result, said Bairlein, “we are discussing something like a silent spring.”
It’s much the same story for many New World migratory species, according to Mike Parr, chief conservation officer for the American Bird Conservancy. For instance, wood thrushes spend the winter in Central America, where many countries have already lost half their original forest cover. The loss of that habitat means that females making the return migration across the Gulf of Mexico may not be fit enough when they arrive in the spring to develop and lay eggs. Moreover, the deep North American forests where the birds like to nest are now highly fragmented, leaving them more vulnerable to predation by raccoons and crows.
So does this mean that our springtime, already much quieter than in the recent past, is doomed to become silent? Both scientists claim to be optimistic. Bairlein travels later this month to a workshop in Nigeria aimed at developing sustainable land use strategies. There’s some evidence, for instance, that acacia trees in the dry habitat just south of the Sahara not only benefit migratory birds but also promote higher soil humidity and thus enable farmers who keep them intact to produce larger crop yields.
Parr also points to small changes that could be a turning point for migratory species. For instance, the forests that now cover large portions of the northeastern region of the United States tend to be about the same age and lack the varied structure many migratory birds need to thrive. But the U.S. Department of Agriculture’s Natural Resources Conservation Service is now working on selective cutting of forests to introduce more varied habitat. “They’ve a very active program,” said Parr. “They don’t want to see species become endangered, because that’s not good for anyone.” It is smarter and far cheaper to save a species before it ends up on the endangered species list.
Both scientists also point to international agreements like the Convention on Biological Diversity, which is now pressuring all 168 signatory countries to meet a 2020 goal of having at least 17 percent of their land area in national parks or other protected areas. “The required political instruments...are already in place,” Bairlein wrote. “We just need to act.”