Teeth have been replaced by beaks... 牙齿被喙取代

166. Feathers, that first evolved to keep dinosaurs warm,
     羽毛最初进化是为帮助恐龙保暖
167. have become specialized for aerial mastery.
     如今已变成驾驭天空的专用工具
168. And that's not the only change.
     这还不只是唯一的变化
169. Teeth have been replaced by beaks...
     牙齿被喙取代
170. ...that allow them to feed on new diets.
     使其能够以新的食物为食
171. But advances in feeding and flight alone
     但仅靠进食与飞行上的进步
172. were not enough to ensure the future of the birds.
     并不足以确保鸟类有一个光明的未来

来自《我们星球上的生命 第一季 第六集 Life on Our Planet S01E06 灰烬中重生》第 169 行