Rotating 16 birds through the positions in a four-duck row, the researchers found outer birds half-asleep during some 32 percent of dozing time versus about 12 percent for birds in internal spots.

研究人员把16只鸟按顺序4只排成一排，发现外面的鸟在32%的时间里处于半睡眠状态，而内部的鸟只有12%的时间处于半睡眠状态。