McCormick Place in Chicago, the largest convention center (会议中心) in North America, is covered in glass that is enjoyable for humans but deadly for birds. On Oct. 5, over 1,000 migrating birds died from colliding with (相撞) its glass walls in a single day.

One key reason for the accident is the glass. During the day, birds fly toward glass as it reflects a perfect image of the sky and nearby trees. As night falls, the bright light from glass buildings attracts birds who fly according to the location of the moon and stars. The collision happened on the night of Oct. 5, when the lights in the building were on for an event.

After colliding with a building, many birds will die on the spot from a broken skull. Others may continue to fly for some distance, but they rarely survive for more than a few hours, as Brendon Samuels, who researches bird window collisions at the University of Western Ontario, Canada, told The Guardian.

Every year, nearly one billion birds collide with glass in the US, according to the US Fish and Wildlife Service. In China, bird collisions are not uncommon, either. In the autumn of 2022 and spring of 2023, the National Anti-bird Collisions Action Alliance reported a total of 190 cases of bird collisions, which included several types of birds listed as second-class protected wildlife.

These tragedies could have been avoided if appropriate measures had been taken. Many places around the world have already put forward bird-related guidelines on building design. These include reducing the use of glass in building walls and applying bird-friendly materials and visual markers to the buildings’ walls. Turning off lights at night during migration seasons can also significantly help reduce bird collisions. Alongside guidelines on bird-friendly building design, people can also do their bit to help birds by putting stickers on glass windows in their homes and closing the curtains at night.

By now, it’s no secret that the phrase “bird brain” should be a compliment, not an insult (侮辱). Some birds are capable of complex cognitive (认知的) tasks, including tool use. Among the brainiest achievements that birds are capable of is vocal (声音的) learning, or the ability to learn to imitate sounds and use them to communicate. In birds, this leads to beautiful calls and songs; in humans, it leads to language. The best flying vocal learners such as parrots also tend to be considered the most intelligent birds. So it’s natural to think that the two characteristics could be linked.

To test whether there is such a link, biologist Jean-Nicolas Audet and his team conducted a massive analysis of 214 birds from 23 species. The researchers developed cognitive tests that could be adapted for different birds. They ultimately presented birds with seven cognitive tasks over six days Four of the tasks tested problem-solving ability. The team then analyzed whether the bird species with more complex vocal learning abilities also performed better on their intelligence tests.

Problem-solving, but not learning or self-control, is strongly associated with more complex vocal learning in birds, the researchers found. “The more advanced vocal learning ability, the more advanced problem-solving skills,” says study co-author Erich Jarvis. Take the tufted titmouse (凤头山雀) for example. This species learns around 63 vocalizations and can learn throughout its life. It completed the problem-solving tasks faster than the brown-headed cowbird, which learns only about nine vocalizations within a set developmental window.

The researchers next hope to search for the genes determining the linked characteristics. That work could further scientists' understanding of how human language evolved. “There is a chance that we will discover genes related to problem-solving and vocal learning that are possibly also used in humans for those same behaviors,” Audet says

I went to the Tsavo National Park in northern Kenya for a film. We set off early for a distant water hole. A huge elephant covered with dry mud, drank calmly and deeply. He might have traveled 50 km to reach the water. He wasn’t going to hurry now. He’d drink a while and rest in the shade, and then drink again or so we thought. What actually happened was that he drank deeply and stepped away. Then he suddenly fell down. Within minutes he was dead.

We called animal doctor Jeremiah Poghon immediately. He removed the head of a poisoned arrow from the elephant’s body, and let out over 100 liters of pus (胺)－the result of the elephant’s meeting with a poacher（偷猎者）months before.

Today's poacher shoots from a blind. He fires an arrow, covered with poison, into the body of an elephant. If the poacher is lucky, the elephant might die in an hour or two; if not, he might have to follow the elephant for days before it dies. Often the arrow head fails to kill the elephant at once－it doesn't mean the poison won't finally kill the ele- phant, but it will be a slow death.

Living in Tsavo through these times, I could see the results of poaching from time to time. When I think about the death of that elephant, what stays with me is the extra- ordinary silence after the shocking sound of his body hitting the ground. I took some comfort from the knowledge that as the dead body returned to the soil, some animals would benefit－but I couldn't escape the feeling that with the death of such a large animal, the world seemed to be a poorer and emptier place.