How many wild whooping cranes are there?

还有多少野生的美洲鹤？

youdao

Sandhill cranes were used in the experiment because whooping cranes are so rare.

先用沙丘鹤做试验，是因为高鸣鹤实在太罕见。

youdao

But if it is a rocky world, its gravity would be about 2.4 times that of Earth - there may be life there, but I wouldn't expect to see anything as gracile as our giraffes or whooping cranes.

BBC: Viewpoint: The obsession with a 'twin Earth'

This makes for spectacular and guaranteed crane viewing, but also means that ongoing projects, including clearing vegetation off the sandbars with heavy machinery each year, are needed to protect this last stretch of habitat, not just for sandhill cranes but also for the endangered whooping cranes who migrate through the area around the same time, and of which there are only 300 left in the wild.

BBC: Nebraska��s awe-inspiring crane migration