Turtles have a habit of eating plastic objects floating in the sea, which may kill them. Many believe that it is because floating plastic bags look similar to jellyfish, which many types of turtles love to eat. However, lots of plastic objects that turtles eat do not look like jellyfish at all. Joseph Pfaller of the University of Florida doubts that the smell of sea micro-organisms（微生物） which live on floating plastic objects attract turtles to eat.

The kind of idea first appeared in 2016. Researchers at the University of California, Davis, noticed that certain chemicals, especially dimethyl sulphide（二甲基硫）, which can be found on plastics where micro-organisms live, are those which many seabirds sniff（嗅）to find food. These birds are more likely to eat plastics.

Since turtles usually appear above the sea surface and sniff the air when going to their feeding areas, Dr. Pfaller believed that they are following these same chemicals like those seabirds and mistakenly think that floating plastic objects are edible.

To test that idea, he and his team did an experiment using loggerhead turtles. They exposed 15 turtles to four smells: the smell of clean water; the smell of turtle-feeding food; the smell of a clean plastic bottle; and the smell of a bottle that had been kept in the ocean for five weeks to allow micro-organisms to grow on it. When sniffing both the smell of turtle-feeding food and that of five-week-old bottles, turtles kept their noses out of the water more than three times as long, and took twice as many breaths as they did when sniffing the smell of fresh bottle-plastic or clean water.

Though they have not yet tested whether dimethyl sulphide on the five-week-old bottles cause turtles to eat plastic objects, Dr. Pfaller and his team think it is highly possible.

Pigeons in London have a bad reputation. Some people call them flying rats. And many blame them for causing pollution with their droppings. But now the birds are being used to fight another kind of pollution in this city of 8. 5 million.

“The problem for air pollution is that it’s been largely ignored as an issue for a long time,” says Andrea Lee, who works for the London-based environmental organization Client Earth. “People don’t realize how bad it is,and how it actually affects their health. ‘‘ London’s poor air quality is linked to nearly 10,000 early deaths a year. Lee says, citing report released by the city manager last year, “If people were better informed about the pollution they’re breathing,” she says,”they could pressure the government to do something about it. ‘‘

Nearby, on a windy hill in London’s Regent’s Park, an experiment is underway that could help-the first week of flights by the Pigeon Air Patrol. It all began when Pierre Duquesnoy, the director for DigitasLBi, a marketing firm, won a London Design Festival contest last year to show how a world problem could be solved using Twitter. Duquesnoy, from France, chose the problem of air pollution.

“Basically, I realized how important the problem was,v he says. “But also I realized that most of the people around me didn’t know anything about it. ‘‘ Duquesnoy says he wants to better measure pollution, while at the same time making the results accessible to the public through Twitter.

“So, “ he wondered, “how could we go across the city quickly collecting as much data as possible?” Drones ( 无人驾驶飞机)were his first thought. But it’s illegal to fly them over London. “But pigeons can fly above London,right?” he says. “They live -actually? they are Londoners as well. So, yeah, I thought about using pigeons equipped with mobile apps. And we can use not just street pigeons, but racing pigeons, because they fly pretty quickly and pretty low. “

So it might be time for Londoners to have more respect for their pigeons. The birds may just be helping to improve the quality of the city's air.

Rescue workers had collected 820 birds from the Gulf of Mexico oil spill, the majority of them already dead. The current spill promises to be the largest in US history, and as cleanup efforts stretch across the summer, it's clear that more oiled birds will be found, stuck and suffering in the black stick liquid. And as they do with every oil spill, rescue workers will go to great lengths to capture and clean the survivors hoping to restore them to their natural habitat.

Is it worth the effort? Some scientists aren’t so sure. Because the stress of being captured and bathed is as significant as the horror of being immersed in oil, and because research suggests that many rescued birds die shortly after being released, some experts say euthanasia (安乐死) is a more humane option.

Clean bird feathers repel water (防水) and regulate body temperature while dirty ones don't. Oil in particular makes feathers heavier and decreases their ability to trap air, which in turn makes birds weak and become easier to drowning, overheating and organ damage. Of course, being captured and cleaned is no picnic either. Some birds wind up returning to their destroyed habitats only to fall victim to the oil again. And those who manage to avoid a second oil bath suffer dramatically shortened life spans (跨度) and lower reproductive success. Of the thousands of birds that were rescued from the Prestige oil spill off the coast of Spain in 2002, only 600 were released into the wild; most of the rest died after just a few days in captivity.

However, bird rescuers say they have learned a lot about how to best help oil-soaked birds, and that therefore, survival rates stand to increase this time around. In the past, birds were cleaned right away, and volunteers often worked through the night bathing rescued birds. But now, captured birds are left to rest for a day or two before being cleaned, and only washed during the day, so as not to disrupt their circadian (生理的) rhythms. But part of that increase may be due to greater selectivity on the part of rescuers. The workers do blood tests right in the field now and birds that are loaded with hydrocarbons (碳氢化合物) or don’t look like they’re going to make it are put down right away, rather than subjected to the stress of captivity and cleaning.

And so far, while release rates may be improving, there is little evidence of better medium or long-term survival, especially for the more-difficult-to-save species. There still aren’t good protocols (协议) for repairing the internal organ damage. Anyway, rescue efforts will continue in large part because the public demands that. Euthanasia is a difficult thing to do, especially for people who have built their lives around saving animals.