Assertion: coot | /r/CapableOf | bob their heads
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Source sentences:
text: Although they do graze on short grass, they spend most of their time in the water, bobbing their heads as they swim and making short dives after a little forward jump.
text: Coots bob their heads while walking, quite likely because the head movements help them to judge the distance to their prey.
text: Appearing somewhat like aquatic pigeons, coots also bob their heads while swimming.