Scientists say a huge percentage of bird species are in danger because their habitats are disappearing.

The scientists studied the migration, or flight, paths, of almost 1,500 species and decided that 91 percent of them passed through dangerous areas. The major danger for migratory birds is development. Building and paving have covered over nature where birds stop and feed as they move from one part of the world to another.

For example, a bird called the bar-tailed godwit migrates from its breeding grounds in the Arctic. It flies all the way to Australia and New Zealand. The problem, according to investigators, is that many of these small birds die along their migration because they don't have a safe place to eat and rest. There is no place to restore their energy for the next part of their journey. "They simply perish along the way," says one of the scientists.

Countries in North Africa, Central Asia and those along the coasts of East Asia are having the most difficult time conserving land. The scientists say these countries do not have enough areas that are safe for birds.

"Our world gets poorer every time we lose a species,’’ one of the scientists says.

The researchers say countries need to work together and come up with safe stopover areas for birds that pass through their boundaries.

For example, one country might have preserved safe zones for migrating birds. But a neighbor country might not. A bird might die.

One scientist who is not involved in the report tells the Los Angeles Times that while some habitats are changing, more work can be done to make urban areas safe for birds. He says small changes—like planting more native plants or keeping cats out of areas birds would be likely to use—could make a big difference.

Everybody loves a fat pay rise. Yet pleasure at your own can vanish if you learn that a colleague has been given a bigger one. Indeed, if he has a reputation for slacking, you might even be angry. Such behaviour is regarded as “all too human”, with the underlying assumption that other animals would not be capable of this finely developed sense of grievance. But a study by Sarah Brosnan and Frans de Waal of Emory University in Atlanta, Georgia, which has just been published in Nature, suggests that it is all too monkey, as well.

The researchers studied the behaviour of female brown capuchin monkeys. They look cute. They are good-natured, co-cooperative creatures, and they share their food readily. Above all, like their female human counterparts, they tend to pay much closer attention to the value of “goods and services” than males.

Such characteristics make them perfect candidates for Dr. Brosnan’s and Dr. de Waal’s study. The researchers spent two years teaching their monkeys to exchange tokens for food. Normally, the monkeys were happy enough to exchange pieces of rock for slices of cucumber. However, when two monkeys were placed in separate but adjoining chambers, so that each could observe what the other was getting in return for its rock, their behaviour became markedly different.

In the world of capuchins, grapes are luxury goods (and much preferable to cucumbers). So when one monkey was handed a grape in exchange for her token, the second was reluctant to hand hers over for a mere piece of cucumber. And if one received a grape without having to provide her token in exchange at all, the other either tossed her own token at the researcher or out of the chamber, or refused to accept the slice of cucumber. Indeed, the mere presence of a grape in the other chamber (without an actual monkey to eat it) was enough to induce resentment in a female capuchin.

The researchers suggest that capuchin monkeys, like humans, are guided by social emotions. In the wild, they are a co-operative, group-living species. Such co-operation is likely to be stable only when each animal feels it is not being cheated. Feelings of righteous indignation(义愤填膺), it seems, are not the preserve of people alone. Refusing a lesser reward completely makes these feelings abundantly clear to other members of the group. However, whether such a sense of fairness evolved independently in capuchins and humans, or whether it stems from the common ancestor that the species had 35 million years ago, is, as yet, an unanswered question.

As a boy, Ramirez Cruz loved hiking with his grandfather up into the mountains of central Mexico. While the old man hunted for wild mushrooms, Ramirez would play among the monarch butterflies that migrated 3,000 miles to this forest each autumn, turning the blue sky into a sea of orange.

Ramirez is 75 now and each winter he still goes looking for butterflies. But these days, he might spend hours searching the forest without catching sight of a single one.

The world is losing monarch butterflies at a surprising rate, as many human activities destroy their natural habitats. But the biggest threat yet has only recently come into focus. Climate change, with its extreme storms, is destroying the forest that serves as the butterfly’s winter home.

To help his beloved butterflies, Ramirez has partnered with scientists on an experiment: They are trying to move an entire forest 1,000 feet up a mountain. He agrees with scientists that it is necessary to create an ecosystem where the butterflies will be able to survive.

Over the last several years, the team of researchers has overseen the relocation(迁移) of about 1,000 trees that were growing at lower altitudes up to higher and cooler areas. Ramirez and the scientists hope to expand the project and establish the trees at even higher altitudes on other nearby mountains if temperatures continue to soar.

After checking on the trees, Ramirez went off to look for the butterflies. He found a few butterflies then a few more. There weren’t as many as he remembered from his childhood, but it was still a sight to see. Ramirez eased himself down to sit on the soft forest floor and watched in silence. The only sound was the whistle of the wind and the gentle flapping(拍打) of their wings.