When migratory bird ecologist Brian Evans first started hearing about dead birds across Washington, D. C. in mid May, he "wrote it off." Bird deaths in the spring are common-only 30 percent of young songbirds typically survive to the next season. And with people stuck at home during the pandemic, "we're noticing these things." Evans says. "Everybody got into birds last year, and then this year they realize birds have awful lives!"

Then, while Evans was in his garden on May 28, his neighbor came over to tell him about a bird she had just found on the road. "It looked like it was blind," she said, "and it was shaking. When she walked up to it, it didn't budge." "That's when this little flash went off in my head saying, that's pretty unusual." Evans says. "That's not your typical dying young birds."

Later that day, a colleague started texting him photos of dead birds. Half an hour after that, another neighbor called him to look at a bird that had crusty (暴躁的) eyes and couldn't balance. "I grabbed it and took it to City Wildlife," he says. "I went in there, and they were like, oh, yeah, this is really serious."

"This event is remarkable," Evans says. "What makes it significant is the number of birds that have been ill or have died and the number of species that have been impacted." Cases have also appeared in a variety of birds. "One American crow was just standing in the street," near his house in May, Evans says. "It was very unusual. It died as I was preparing to take it to City Wildlife."

However, total and even statewide numbers remain tricky to determine, says Evans. "I'm still desperately trying to understand the distribution of the epidemic", he says.

On July 2, the US Geological Survey, which is working with wildlife agencies in the affected states, announced that "no definitive causes of illness or death have been determined at this time."

Honeybees rely heavily on flower patterns not just colors when searching for food, new research shows.

A team led by the University of Exeter tested bee behaviour and built bee’s-eye-view simulations (模拟装置) to work out how they see flowers.

Honeybees have low resolution vision, so they can only see a flower’s pattern clearly when they are within few centimeters. However, the new’ study shows bees can very effectively distinguish between different flowers by using a combination of colour and pattern.

In a series of tests, bees rarely ignored pattern, suggesting colour alone does not lead them to flowers. This may help to explain why some colours that are visible to bees are rarely produced by flowers in nature.

“We studied a large amount of data on plants and bee behaviour,” said Professor Natalie Hempel, from Centre for Research in Animal Behaviour. “By training and testing bees using man-made patterns of shape and colour, we found they relied flexibly on their ability to see both of these elements. Showing how insects see colour and learn colour patterns is important to understand how pollinators (传粉者) may, or may not, create evolutionary ‘pressures’ on the colours and patterns that flowers have evolved (进化). Our findings suggest that flowers don’t need to evolve too many different flower colours, because they can use patterns to vary their displays so bees can tell them apart from other flowers.”

One typical feature identified in the study is that the outside edges of flowers usually contrast strongly with the plant’s leaves while the centre of the flower does not have such a strong contrast with the leaf colour. This could help bees quickly identify colour differences and find their way to flowers.

While flowers may be beautiful to humans, Professor Hempel stressed that understanding more about bees and the threats they face meant we need to see the world “through the eyes of a bee and the mind of a bee.”