Other animals such as hummingbirds enter hyperphagia before long migration periods.

其他动物，如蜂鸟，在长时间迁徙之前就进入了食欲过度状态。

This means the overall total is now around 60,000, and this is before the peak migration period over the summer.

这意味着现在的总数约为 60, 000 只， 而这是在夏季迁徙高峰期之前。

What Sheela discovered was a story of mass migration – periods in history when large groups of people move from one geographical area to another.

希拉所发现的是一个大规模人口流动的故事——历史上大批人从一个地理区域迁移到另一个地理区域的时期。

I was just so obsessed with this; I couldn't bear not being out in the field for one of the migration periods... Each year I was going out and doing this more and more, so I was accumulating all these tapes.

埃文斯：我只是太痴迷于这个;我无法忍受在其中一个迁移期间不在野外......每年我都越来越多地出去做这件事，所以我积累了所有这些磁带。