Birds are indicators of the environment. If they are in trouble, we know we'll soon be in trouble.
鸟类是环境的指示器。如果他们有麻烦,我们知道我们很快就会有麻烦。
Birds are indicators of the environment. If they are in trouble, we know we'll soon be in trouble.
鸟类是环境的指示器。如果他们有麻烦,我们知道我们很快就会有麻烦。