If the ants are in the midst of moving to a new bivouac site, the bird follows the immigration column from the old site to the new site. “In a sense, it’s putting the ants to bed before returning to its roost,” says O’Donnell, “which is what researchers do.” Early the next morning, the bird flies directly to the bivouac, lands on a nearby perch, sometimes only inches from the ants, and peers into the bivouac and the ground around it to assess the ants’ activity. If the ants are raiding, the bird will track the raid to its front and forage there; if there is no activity, it will move on to
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