greyback

例句：

1. 1. Thegreybacks are a common sight inthe park.
   公园里常见的灰色背影。
2. 2.The greybacks were spotted on theroadside.
   在路边发现了灰色背影。
3. 3.The greybacks are believed to bea species of bird.
   灰色背被认为是一种鸟类。