that for most of the year they would be unable to cross it. 它们一年中大部分时间都无法穿越这里

180. and are on their way north to the southern United States.
     正向北飞往美国南部
181. To get there, they have to cross the Sonoran desert.
     要想到达那里 它们必须穿越索诺兰沙漠
182. But the desert is so big
     不过这片沙漠很大
183. that for most of the year they would be unable to cross it.
     它们一年中大部分时间都无法穿越这里
184. Now, with the saguaro in bloom,
     现在 有了正在开花的弁庆柱
185. they can refuel on the way.
     它们便能在旅途中得到休整
186. So the saguaro's success in developing a way to store water
     看来弁庆柱进化出的 这种成功的储水方式

来自《行星地球 第一季 第五集 Planet Earth S01E05 沙漠》第 183 行