Standing out from the crowd isn't always a good thing.

Birds with uncommon traits like big beaks(喙), long tails and extended wings are more likely to be threatened and face extinction, new research finds. 

"We are fascinated by the diversity of the planet's bird species. At the same time, we are deeply concerned about the threats these birds face," lead author Jarome Ali, a PhD candidate at Princeton University, says. Ali completed the research at Imperial College London.

For their work, researchers analyzed measurement data collected from 9, 943 bird species, which are about 99% of all living bird species. The information came from both living birds as well as museum specimens(标本). The measurements included beak size and shape, as well as the length of legs, tails and wings. Researchers combined the information on physical traits with the birds' risk of extinction. Next, they ran simulations(模拟) about what would occur if the most threatened birds were to become extinct.

"All our simulations showed that extinction has worse effects on the diversity of bird shapes than we expected. This is deeply concerning, but not shocking given that we first found that threatened birds were more unique than non-threatened birds," Ali says.

The researchers weren't sure what could explain the link between unusual birds and their extinction risk. "Unique birds are likely to play specialized roles in the ecosystem. One possible explanation is that as habitats come under threat, these specialized roles are likely to be the first to be targeted," Ali says. "For example, if you were a hummingbird and specialized to feed on a small subset of plants, then damage to your habitat would be worse than if you were a less unique bird that eats a whole range of foods."

"The loss of these rare birds has an impact on the environment because their role in the ecosystem is lost," Ali says. "Our findings imply that we cannot simply hope that non-threatened species will come in and fill the role of the threatened species."