【推荐2】The color of food might affect just how much you want to eat them，but what about the birds in your neighborhood？Would they care what color their food is？Try this out for a science fair project，or just to learn something new while making your local birds happy.

Begin this experiment with the question“What color of birdseed（鸟食），if any，will birds like the most?”, and then make a hypothesis (假设) based on your question. An example might be“Birds will eat more green birdseed than other colors of birdseed.”

You should get several bird feeders. Purchase birdseed that is very light in color. To color the birdseed, pour it into a bowl and then add food coloring that you can purchase from the store. Mix them up well with a spoon and continue to add coloring until all the seed is colored. You should sample at least a few colors and have one feeder with seed that has not been colored—this is called the control and it will give you something to compare your results to. Now just hang them up outside in the same location，and wait for your feathered friends to show up. This works best in an area where birds are used to feeding from a feeder—it can take birds over a week to find new feeders.

Observe your bird feeders whenever possible，and keep track of how much seed is in each bird feeder each day. A ruler is helpful for this. You might also want to take pictures of the feeders and keep track of what kind of birds visit each feeder. Over time，you should be able to see if one color of seed gets eaten more than others.

Once your experiment is done，you will be able to go back to your hypothesis and see if it is correct. Remember, it’s not bad if your hypothesis was wrong. The main thing is that you’ve learned something from your experiment，and hopefully you had some fun doing it.

【推荐1】Summer brings flowers and dirt and barbeque smoke. In the most wintery places, there isn’t much outside on cold days except snow, strong wind and cars warming up. Pine needles, wood smoke and snow---these are the smells of winter, and for people who live with different seasons, wintry weather brings its own set of olfactory(嗅觉的) experiences. But why does the cold of winter smell different from the heat of summer?

One reason is that odor (气味) molecules move much more slowly as the air temperature drops, said Pamela Dalton, an olfactory scientist at the Monell Chemical Senses Center in Philadelphia. That means that there are simply fewer smells to smell on a cold, crisp day than there are on a hot and humid one. It’s the same reason why hot soup smells more than cold soup does and why the garbage truck leaves behind the strongest smells on steamy summer days.

What’s more, our noses don’t work quite well when the surrounding air is cold, Dalton said. In experiments that require biopsies(活组织检查) of olfactory receptors that lie deep inside the nose, researchers at Monell have discovered that the receptors “bury themselves a little more deeply in the nose in winter,” she said, “possibly as a protective response against cold, dry air.”

There is a strong psychological factor in our sense of smell, Hirsch added, and what we expect to smell has a big influence on what we actually smell. In The Invalid’s Story by Mark Twain, for example, a man is stuck on a train next to what he thinks is a rotting dead body but is actually a box of cheese that smells extremely unpleasant. So strongly affected by the smell, he spends too long looking for fresh air on the freezing platform and develops a fever that ends up killing him. “What you think of a smell have powerful effects on you whether you like it and whatever you think it to be,” Hirsch said. “So, if you go outside in winter and you are used to smelling snow or nuts in the fire or whatever you happen to smell outside, that’s what you will interpret smells to be.”

To cope with lack of smells in winter, many people try to burn more candles with pleasant smell, cook more sweet stews(炖菜) and bake more cookies, which creates a greater contrast between the indoor and outdoor environments. “You’re probably fond of indoor smells in the winter,” Dalton said. “Homes are closed up, and windows are closed. We concentrate on the smells of cooking and living.”

【推荐3】In a world on fire and underwater, scientists have announced some good news: Several important tuna species have stepped back from the edge of extinction.

Two bluefin tuna species, a yellowfin, and an albacore are no longer seriously endangered or have moved off the leading international list of endangered species entirely.

The unexpectedly fast recovery speaks to the success of efforts over the past decade to end overfishing. But tuna are not the only species scientists are thinking carefully at the 2021 World Conservation Congress in Marseille, France, which is organized by the International Union for Conservation of Nature (IUCN). Researchers warn that many other sea species continued to be imperiled. For example, more than a third of the world’s sharks are still threatened with extinction due to overfishing, habitat loss, and climate change.

“I think the good news is that sustainable fishing industry are possible,” says Beth Polidoro, a biologist at Arizona State University. “We can eat fish without reducing the population to the point where it is on the road to dying out or extinction.” At the same time, she warns that the recovery should not encourage us to catch as many fish as we want. “We need to keep doing what’s working.” Polidoro adds.

The IUCN, which determines the world’s most endangered species on its Red List of Threatened Species, also announced at the meeting that some animals are moving in the other direction, onto the Red List. Like the Komodo dragon, a lizard, it is at particular risk from climate change.

Of course, the work of protection is never over, and it will require close and continuous attention to make sure neither tuna nor Komodo dragons return to the edge of dying out. But for now, people can celebrate a few wins for the animal world.