Krebs has discovered that great blue herons look up more often when in smaller flocks than when in larger ones, solely as a consequence of poor feeding conditions.
克雷布斯发现，大蓝鹭在较小的群体中比在较大的群体中更容易抬头，这完全是由于恶劣的饲养条件造成的。
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Krebs hypothesizes that the herons in smaller flocks are watching for herons that they might follow to better feeding pools, which usually attract larger numbers of the birds.