Play appears to be a developmental characteristic of animals with fairly sophisticated nervous systems, mainly birds and mammals.

玩耍似乎是具有相当复杂的神经系统的动物（主要是鸟类和哺乳动物）的一种发育特征。

youdao

Like birds and mammals that eat the fish and insects, and you get trees and plants that begin to grow near the standing water that can't grow near the running water.

就像鸟类和哺乳动物吃鱼和昆虫，你可以看到树木和植物开始在静水附近生长，而不能生长在流动的水附近。

youdao

It's now believed yawning operates like a radiator for birds and mammals.

现在他们明白了呵欠对于鸟类和哺乳类来说起到了散热器的作用。

youdao

And then you have issues such as birds and mammals coated with oil."

VOA: standard.2010.05.09

From a psychological point then, animals have evolved to be nice to their kin, particularly their children, and particularly in birds and mammals.

从心理学角度看，动物进化趋向于对自己的亲人有益，特别是自己的孩子，以鸟类和哺乳类为代表。

耶鲁公开课 - 心理学导论课程节选

Birds and mammals invest in quality and not quantity, as opposed to fish and reptiles.

鸟类和哺乳类靠质生存,而非以量取胜，这与鱼类和两栖类不同。

耶鲁公开课 - 心理学导论课程节选

Slugs and seals prospered but bees, birds and mammals struggled, with bats particularly hard hit.

BBC: Purple hairstreak butterfly numbers hit by wet weather

Spinosad is an environmental "reduced-risk" oral insecticide that has little effect on other insects, birds and mammals.

BBC: The malaria parasite is spread by mosquitoes

It revealed, contrary to the Chernobyl Forum's 2005 report, that biodiversity in insects, birds and mammals is declining.

CNN: Chernobyl: Environmental dead zone or eco-haven?