In the middle of the 19th century, more than 50,000 crested ibis were walking on their stilty legs through waterways across East Asia, everywhere from China and Russia to Korea and Japan. By 1981, only five of these long-beaked, red-faced birds were thought to remain.
Overhunting and habitat loss caused the population to collapse—hard. In 1963, the last crested ibis disappeared from Russia (without love). In 1975, North Korea declared the birds locally extinct. The five known survivors were all in Japan, where scientists caught the birds in a desperate attempt to set up a captive breeding program. It was not to be. The program failed, and the last known ibis on earth faded away without producing a single heir.
Fortunately, the rumors of the crested ibis’s extinction turned out to be slightly exaggerated. Later in 1975, a small band of seven survivors turned up in the foothills of China’s Qinling Mountains. The race was back on to save the species.
To its credit, China took the rediscovery of crested ibis extremely seriously. The government immediately established the Hanzhong Crested Ibis National Nature Reserve to protect the birds’ habitat. It also instituted strict guidelines about pesticides and development, set up a monitoring station for every nest, and implemented GPS-based systems to keep track of individuals. In time, conservationists took some of the birds in to give captive breeding another try.
It worked. From those seven ibis—four adults and three chicks—the species was reborn. Currently, China’s birds number around 2,000 and Japan’s wild population sits at about 150. The crested ibis is still endangered, but after decades of steadfast conservation efforts, the birds have established a foothold.
The crested ibis’s grip on existence, of course, is tenuous. But according to a new study, the bird is lucky to have a friend in the avian world to watch its back. I’m talking about the little egret.
The little egret is another Asian bird with long legs and a penchant for hunting in shallow rivers and flooded rice patties. In fact, both species relish eating fish, frogs, and other small animals. This might make you think that they are competitors and a threat to each other’s continued existence. But according to a study published last month in The Auk: Ornithological Advances, the opposite seems to be true.
The researchers found that when ibis and egrets forage together, they may actually be safer from predators like hawks, crows, and snakes.
There are two ways this could come about, says Kartik Shanker, an evolutionary ecologist and director of the Ashoka Trust for Research in Ecology and the Environment in Bangalore, India. First, there is truth to the old adage that there’s safety in numbers, says Shanker, who was not involved in the study. Simply put, the more birds in your flock, the less likely you are to get eaten. And that holds true even when your flock is a mishmash of species. What’s more, the benefit of increased safety seems to outweigh the cost of hanging out with birds who might sometimes steal your lunch.
The birds’ differences in foraging strategies also give them an advantage. You see, ibis are what scientists call tactile foragers, which means they feel around for food underwater with their long bills. Meanwhile, egrets are visual foragers that spy prey before stalking and snatching their victims. (There are tons of videos on the web of egrets devouring small animals, by the way.)
Frogs and gophers (!) might not be the only things egrets catch with their keen eyesight, though. The researchers wanted to test how good they are at detecting predators. So they spent two months in the Qinling Mountains attempting to spook mixed and unmixed flocks of crested ibis and recording the results.
As it turns out, crested ibis in mixed-species flocks do tend to become alert to threats sooner than ibis in groups of their own. This jibes with what we already know about mixed flocks, says Shanker, whose student Hari Sridhar conducted a synthesis of mixed-flock studies in 2009. In addition to anti-predator benefits, Shanker says, mixed flocks can help birds forage more efficiently. This might mean flushing prey toward each other, even inadvertently, or discovering new prey bases for the group.
“There is also an indirect foraging benefit, as less time spent being vigilant can mean more time for foraging,” Shanker says.
What does all this mean for crested ibis conservation? Well, the authors suggest that conserving habitats that are favorable for egrets and other species may help ibis survive. Furthermore, protecting areas that are used by egrets but not ibis—such as the cliffs egrets sometimes use to nest—could eventually pay back into crested ibis conservation by working to preserve the ibis’s allies.
“In conservation, we often protect one species at a time but forget that some relationships with other species are crucial,” says Guy Beauchamp, a biologist at the University of Montreal and an expert on group living in birds.
Shanker is a little more reserved when it comes to the idea that egrets may be the key to saving ibis, but he admits that a better understanding of the biology of a species is critical if we hope to protect it. “In general, I think the role of mixed-species groups in communities has not been given due importance,” he says.
Clearly, saving the endangered birds from pollution, hunting, and habitat destruction remain keys to preventing another brush with extinction. But protecting their feathered friends will give the crested ibis a leg up, too.
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